MAX1790EUA原理图各脚功能电路原理芯片引脚定义引脚图及功能-中国IC网-芯三七

当前位置：IC37首页_>M字母起始型号索引_>M字母起始型号索引第966页更新时间：2024-10-25 17:33:19

产品型号MAX1790EUA的概述

MAX1790EUA概述 MAX1790EUA是一款高性能的集成电路，专为电池管理和电源监控应用设计。该芯片是由美国半导体制造商Maxim Integrated Products（现为Analog Devices的一部分）生产，主要用于提供精确的电压和电流监测。其高集成度和小型封装使其非常适合便携式设备以及对空间有严格要求的应用。 MAX1790EUA的基本功能包括电压检测、电流监测和多种状态指示。这些功能使得它能够广泛应用于各种电池供电的设备中，比如智能手机、平板电脑、无线耳机等。此外，该芯片还具备低功耗特性，能够提高设备的整体能效。详细参数以下是MAX1790EUA的一些重要技术参数： - 工作电压：2.7V至5.5V - 温度范围：-40℃至+125℃ - 电流测量精度：±1% - 电压测量精度：±0.5% - 最大电流测量范围：100mA - 典型电流消耗：75μA - 封...

产品型号MAX1790EUA的Datasheet PDF文件预览

19-1563; Rev 3; 9/05

Low-Noise Step-Up DC-DC Converters

General Description

Features

The MAX1790/MAX8715 boost converters incorporate

high-performance (at 1.2MHz), current-mode, fixed-fre-

quency, pulse-width modulation (PWM) circuitry with a

built-in 0.21Ω/0.15Ω n-channel MOSFET to provide a high-

ly efficient regulator with fast response.

♦ 90% Efficiency

♦ Adjustable Output from V to 12V

♦ 1.6A, 0.21Ω, 14V Power MOSFET (MAX1790)

♦ 2.4A, 0.15Ω, 14V Power MOSFET (MAX8715)

♦ +2.6V to +5.5V Input Range

High switching frequency (640kHz or 1.2MHz selectable)

allows easy filtering and faster loop performance. An

external compensation pin provides the user flexibility in

determining loop dynamics, allowing the use of small, low

equivalent-series-resistance (ESR) ceramic output capaci-

tors. The device can produce an output voltage as high as

12V from an input as low as 2.6V.

♦ Pin-Selectable 640kHz or 1.2MHz Switching

Frequency

♦ 0.1µA Shutdown Current

♦ Programmable Soft-Start

♦ Small 8-Pin µMAX Package

Soft-start is programmed with an external capacitor, which

sets the input-current ramp rate. In shutdown mode, cur-

rent consumption is reduced to 0.1µA. The MAX1790/

MAX8715 are available in a space-saving 8-pin µMAX^®

package. The ultra-small package and high switching fre-

quency allow the total solution to be less than 1.1mm high.

Ordering Information

µMAX is a registered trademark of Maxim Integrated Products,

PART

TEMP RANGE

-40°C to +85°C

PIN-PACKAGE

8 µMAX

Inc.

MAX1790EUA

MAX1790EUA+

MAX8715EUA

MAX8715EUA+

Applications

8 µMAX

LCD Displays

8 µMAX

PCMCIA Cards

8 µMAX

Portable Applications

Hand-Held Devices

+ Denotes lead-free package.

Typical Operating Circuit

Pin Configuration

2.6V TO 5V

TOP VIEW

COMP

OUT

FREQ

ON/OFF

SHDN

MAX1790

MAX8715

SHDN

GND

MAX1790

MAX8715

FREQ

GND

μMAX

COMP

________________________________________________________________ Maxim Integrated Products

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Low-Noise Step-Up DC-DC Converters

ABSOLUTE MAXIMUM RATINGS

LX to GND ..............................................................-0.3V to +14V

Operating Temperature Range

IN, SHDN, FREQ, FB to GND ................................-0.3V to +6.2V

MAX1790EUA/MAX8715EUA ........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range.............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

SS, COMP to GND.......................................-0.3V to (V + 0.3V)

RMS LX Pin Current ..............................................................1.2A

Continuous Power Dissipation (T = +70°C)

8-Pin µMAX (derate 4.1mW/°C above +70°C).............330mW

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional

operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to

absolute maximum rating conditions for extended periods may affect device reliability.

ELECTRICAL CHARACTERISTICS

(V = SHDN = 3V, FREQ = GND, T = 0°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)

PARAMETER

Input Supply Range

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

2.6

5.5

rising, typical hysteresis is 40mV,

Undervoltage Lockout

UVLO

2.25

2.38

2.52

LX remains off below this level

= 1.3V, not switching

= 1.0V, switching

0.18

0.35

MAX1790

Quiescent Current

µA

= 1.3V, not switching

= 1.0V, switching

0.21

2.5

0.1

0.35

5.0

MAX8715

Shutdown Supply Current

ERROR AMPLIFIER

Feedback Voltage

SHDN = GND

Level to produce V

= 1.24V

COMP

1.222

1.24

1.258

MAX1790

MAX8715

FB Input Bias Current

= 1.24V

125

190

Feedback-Voltage Line

Regulation

Level to produce V

2.6V < V < 5.5V

= 1.24V,

COMP

0.05

0.15

%/V

MAX1790

MAX8715

140

160

700

240

Transconductance

ΔI = 5µA

µS

Voltage Gain

V/V

OSCILLATOR

FREQ = GND

540

1000

640

1220

740

1500

Frequency

kHz

OSC

FREQ = IN

FREQ = GND

Maximum Duty Cycle

FREQ = IN

N-CHANNEL SWITCH

= 1V,

MAX1790

MAX8715

1.2

1.8

1.6

2.4

2.3

3.4

Current Limit

duty cycle =

65% (Note 1)

LIM

MAX1790

MAX8715

0.21

0.15

0.01

0.5

0.35

On-Resistance

MAX1790

MAX8715

Leakage Current

= 12V

µA

LXOFF

_______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

ELECTRICAL CHARACTERISTICS (continued)

(V = SHDN = 3V, FREQ = GND, T = 0°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)

PARAMETER

SYMBOL

CONDITIONS

MIN

0.30

0.20

TYP

0.45

0.30

MAX

0.65

0.43

UNITS

MAX1790

MAX8715

Current-Sense Transresistance

V/A

SOFT-START

Reset Switch Resistance

Charge Current

100

7.0

= 1.2V

1.5

µA

CONTROL INPUTS

Input Low Voltage

Input High Voltage

Hysteresis

SHDN, FREQ

0.3 x V

0.7 x V

1.8

0.1 x V

FREQ Pulldown Current

SHDN Input Current

9.0

µA

FREQ

0.001

SHDN

ELECTRICAL CHARACTERISTICS

(V = SHDN = 3V, FREQ = GND, T = -40°C to +85°C, unless otherwise noted.) (Note 2)

PARAMETER

Input Supply Range

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

2.6

5.5

rising, typical hysteresis is 40mV,

Undervoltage Lockout

UVLO

2.25

2.52

LX remains off below this level

= 1.3V, not switching

= 1.0V, switching

0.35

MAX1790

Quiescent Current

µA

= 1.3V, not switching

= 1.0V, switching

0.35

MAX8715

Shutdown Supply Current

ERROR AMPLIFIER

Feedback Voltage

SHDN = GND

Level to produce V

= 1.24V

COMP

1.215

1.24

1.260

MAX1790

MAX8715

FB Input Bias Current

= 1.24V

190

Feedback-Voltage Line

Regulation

Level to produce V

2.6V < V < 5.5V

= 1.24V,

COMP

0.15

%/V

µS

MAX1790

MAX8715

260

Transconductance

OSCILLATOR

ΔI = 5µA

FREQ = GND

FREQ = IN

490

900

770

1500

Frequency

kHz

OSC

Maximum Duty Cycle

FREQ = GND

_______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

ELECTRICAL CHARACTERISTICS (continued)

(V = SHDN = 3V, FREQ = GND, T = -40°C to +85°C, unless otherwise noted.) (Note 2)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

N-CHANNEL SWITCH

= 1V,

MAX1790

MAX8715

1.2

1.8

2.3

3.0

Current Limit

duty cycle =

65% (Note 1)

LIM

MAX1790

MAX8715

MAX1790

MAX8715

0.5

On-Resistance

0.35

0.65

0.43

0.30

0.20

Current-Sense Transresistance

V/A

CONTROL INPUTS

Input Low Voltage

Input High Voltage

SHDN, FREQ

0.3 x V

0.7 x V

Note 1: Current limit varies with duty cycle due to slope compensation. See the Output-Current Capability section.

Note 2: Specifications to -40°C are guaranteed by design and not production tested.

_______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

Typical Operating Characteristics

(Circuit of Figure 1, V = 3.3V, f

= 640kHz, T = +25°C, unless otherwise noted.)

OSC A

MAX1790 EFFICIENCY

vs. OUTPUT CURRENT

MAX1790 EFFICIENCY

vs. OUTPUT CURRENT

MAX1790 EFFICIENCY

vs. OUTPUT CURRENT

= 640kHz

OSC

L = 5.4μH

= 640kHz

OSC

L = 10μH

= 640kHz

L = 10μH

OSC

= 1.2MHz

OSC

L = 5.4μH

= 1.2MHz

OSC

L = 2.7μH

= 3.3V

= 5V

= 12V

= 3.3V

= 12V

OUT

100

1000

100

1000

100

1000

OUTPUT CURRENT (mA)

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX1790 OUTPUT VOLTAGE

vs. OUTPUT CURRENT

MAX8715 EFFICIENCY

vs. OUTPUT CURRENT

12.10

12.05

12.00

11.95

11.90

11.85

11.80

11.75

11.70

11.65

11.60

0.7

= 9V

= 1.2MHz

L = 6.8μH

OUT

= +85°C

OSC

0.6

0.5

0.4

0.3

0.2

0.1

= 640kHz

OSC

= +25°C

= 1.2MHz

OSC

= -40°C

= 5.0V

= 3.3V

= 12V

= 640kHz

OUT

OSC

2.5

3.0

3.5

4.0

4.5

5.0

5.5

20 40 60 80 100 120 140 160 180 200

OUTPUT CURRENT (mA)

100

1000

INPUT VOLTAGE (V)

OUTPUT CURRENT (mA)

_______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

Typical Operating Characteristics (continued)

(Circuit of Figure 1, V = 3.3V, f

= 640kHz, T = +25°C, unless otherwise noted.)

OSC

MAX8715

PULSED LOAD-TRANSIENT RESPONSE

MAX1790 LOAD-TRANSIENT RESPONSE

MAX8715 LOAD-TRANSIENT RESPONSE

200mA

CH1

200mA

CH1

40mA

= 120kΩ

= 1200pF

COMP

= 82kΩ

= 750pF

COMP

= 56pF

COMP2

10mA

= 10pF

COMP2

CH2

CH3

CH2

CH3

CH2

CH3

100μs/div

40μs/div

10μs/div

CH1 = LOAD CURRENT, 100mA/div

CH2 = OUTPUT VOLTAGE, AC-COUPLED, 200mV/div

CH3 = INDUCTOR CURRENT, 1A/div

CH1 = LOAD CURRENT, 200mA/div

CH2 = OUTPUT VOLTAGE, AC-COUPLED, 100mV/div

CH3 = INDUCTOR CURRENT, 500mA/div

CH1 = LOAD CURRENT, 1A/div

CH2 = OUTPUT VOLTAGE, AC-COUPLED, 100mV/div

CH3 = INDUCTOR CURRENT, 500mA/div

= 3V

= 3.3V, V

= 9.0V

= 3.3V, V

= 9.0V

OUT

= 12V, f

= 640kHz, C

= 33μF + 0.1μF

OUT

= 1.2MHz, L = 6.8μH, C

= 3 x 3.3μF

OUT

OSC

= 1.2MHz, L = 6.8μH, C

= 3 x 3.3μF

OUT

OSC

STARTUP WAVEFORM

WITH SOFT-START

MAX1790 STARTUP WAVEFORM

WITHOUT SOFT-START

MAX1790 LOAD-TRANSIENT RESPONSE

500mA

CH1

20mA

= 62kΩ

= 820pF

COMP

CH1

CH2

CH1

CH2

= 56pF

COMP2

CH2

CH3

100μs/div

1ms/div

100μs/div

CH1 = LOAD CURRENT, 500mA/div

CH2 = OUTPUT VOLTAGE, AC-COUPLED, 200mV/div

CH3 = INDUCTOR CURRENT, 1A/div

CH1 = SHDN, 5V/div

CH2 = OUTPUT VOLTAGE, 5V/div

CH3 = INDUCTOR CURRENT, 200mA/div

CH1 = SHDN, 5V/div

CH2 = OUTPUT VOLTAGE, 5V/div

CH3 = INDUCTOR CURRENT, 1A/div

= 5V, f

= 640kHz, C

= 47μF + 0.1μF

OUT

OSC

OUT

= 12V, I

= 10mA, f

= 640kHz,

= 3.3V, V

= 12V, I

= 10mA, f

= 640kHz

OSC

OUT

OSC

OUT

= 0.027μF, C

= 33μF

NO SOFT-START CAPACITOR, C

= 33μF

OUT

_______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

Typical Operating Characteristics (continued)

(Circuit of Figure 1, V = 3.3V, f

= 640kHz, T = +25°C, unless otherwise noted.)

OSC

STARTUP WAVEFORM

WITH SOFT-START

SWITCHING WAVEFORM

CH1

CH2

CH1

CH2

CH3

500ns/div

2ms/div

CH1 = LX SWITCHING WAVEFORM, 5V/div

CH2 = OUTPUT VOLTAGE, AC-COUPLED, 200mV/div

CH3 = INDUCTOR CURRENT, 1A/div

CH1 = SHDN, 5V/div

CH2 = V 5V/div

OUT,

CH3 = INDUCTOR CURRENT, 500mA/div

= 12V, I = 200mA, f = 640kHz,

= 12V, I

= 200mA, f

= 640kHz, L = 10μH;

OUT

OSC

OUT

OSC

= 33μF + 0.1μF

OUT

= 0.027μF

MAX8715 MAXIMUM OUTPUT CURRENT

vs. INPUT VOLTAGE

MAX1790 MAXIMUM OUTPUT CURRENT

vs. INPUT VOLTAGE

1800

= 9V

OUT

1600

1400

1200

1000

800

1600

1400

1200

1000

800

= 1.2MHz

OSC

L = 6.8μH

= 3 x 3.3μF

= 5V

OUT

= 12V

OUT

600

400

200

600

400

200

= 640kHz

OSC

3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0

INPUT VOLTAGE (V)

3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0

INPUT VOLTAGE (V)

_______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

Pin Description

NAME

FUNCTION

Compensation Pin for Error Amplifier. Connect a series RC from COMP to ground. See the Loop

Compensation section for component selection guidelines.

COMP

Feedback Pin. Reference voltage is 1.24V nominal. Connect an external resistor-divider tap to FB and

minimize the trace area. Set V

according to: V

= 1.24V (1 + R1 / R2). See Figure 1.

OUT

SHDN

GND

Shutdown Control Input. Drive SHDN low to turn off the MAX1790/MAX8715.

Ground

Switch Pin. Connect the inductor/catch diode to LX and minimize the trace area for lowest EMI.

Supply Pin. Bypass IN with at least a 1µF ceramic capacitor directly to GND.

Frequency Select Input. When FREQ is low, the oscillator frequency is set to 640kHz. When FREQ is high,

the frequency is 1.2MHz. This input has a 5µA pulldown current.

FREQ

Soft-Start Control Pin. Connect a soft-start capacitor (C ) to this pin. Leave open for no soft-start. The soft-

start capacitor is charged with a constant current of 4µA. Full current limit is reached after t = 2.5 x 10 C

The soft-start capacitor is discharged to ground when SHDN is low. When SHDN goes high, the soft-start

capacitor is charged to 0.5V, after which soft-start begins.

Detailed Description

V_IN

C_IN

2.6V TO 5.5V

The MAX1790/MAX8715 are highly efficient power sup-

plies that employ a current-mode, fixed-frequency

PWM architecture for fast transient response and low-

noise operation. The device regulates the output volt-

age through a combination of an error amplifier, two

comparators, and several signal generators (Figure 2).

The error amplifier compares the signal at FB to 1.24V

and varies the COMP output. The voltage at COMP

determines the current trip point each time the internal

MOSFET turns on. As the load varies, the error amplifier

sources or sinks current to the COMP output according-

ly to produce the inductor peak current necessary to ser-

vice the load. To maintain stability at high duty cycle, a

slope-compensation signal is summed with the current-

sense signal.

10μF

6.3V

V_OUT

ON/OFF

V_IN

SHDN

MBRS130LT1

MAX1790

MAX8715

1.2MHz

0.1μF*

C_OUT

FREQ

GND

640kHz

COMP

0.027μF

At light loads, this architecture allows the ICs to “skip”

cycles to prevent overcharging the output voltage. In

this region of operation, the inductor ramps up to a

fixed peak value (approximately 50mA, MAX1790 or

75mA, MAX8715), discharges to the output, and waits

until another pulse is needed again.

C_COMP2

R_COMP

C_COMP

* OPTIONAL

Figure 1. Typical Application Circuit

_______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

SKIP

COMPARATOR

4μA

SHDN

BIAS

SOFT-

START

SKIP

COMP

ERROR

AMPLIFIER

ERROR

COMPARATOR

∞

CONTROL

AND DRIVER

LOGIC

1.24V

CLOCK

GND

SLOPE

COMPEN-

SATION

CURRENT

SENSE

FREQ

OSCILLATOR

5μA

MAX1790

MAX8715

Figure 2. Functional Diagram

after the soft-start cycle is completed. When the shut-

down pin is taken low, the soft-start capacitor is

discharged to ground.

Output-Current Capability

The output-current capability of the MAX1790/MAX8715

is a function of current limit, input voltage, operating fre-

quency, and inductor value. Because of the slope com-

pensation used to stabilize the feedback loop, the duty

cycle affects the current limit. The output-current capa-

bility is governed by the following equation:

Frequency Selection

The MAX1790/MAX8715s’ frequency can be user

selected to operate at either 640kHz or 1.2MHz.

Connect FREQ to GND for 640kHz operation. For a

1.2MHz switching frequency, connect FREQ to IN. This

allows the use of small, minimum-height external com-

ponents while maintaining low output noise. FREQ has

an internal pulldown, allowing the user the option of

leaving FREQ unconnected for 640kHz operation.

= [I

x (1.26 - 0.4 x Duty) -

LIM

OSC

OUT(MAX)

0.5 x Duty x V / (f

x L)] x η x V / V

IN OUT

where:

= current limit specified at 65% (see the Electrical

LIM

Characteristics)

Duty = duty cycle = (V

- V + V

) /

Shutdown

The MAX1790/MAX8715 are shut down to reduce the

supply current to 0.1µA when SHDN is low. In this

mode, the internal reference, error amplifier, compara-

tors, and biasing circuitry turn off while the n-channel

MOSFET is turned off. The boost converter’s output is

connected to IN by the external inductor and catch

diode.

OUT

DIODE

)

- I

x R

+ V

OUT LIM

DIODE

= catch diode forward voltage at I

LIM

DIODE

η = conversion efficiency, 85% nominal

Soft-Start

The MAX1790/MAX8715 can be programmed for soft-

start upon power-up with an external capacitor. When the

shutdown pin is taken high, the soft-start capacitor (C

)

Applications Information

is immediately charged to 0.5V. Then the capacitor is

charged at a constant current of 4µA (typ). During this

time, the SS voltage directly controls the peak inductor

Boost DC-DC converters using the MAX1790/MAX8715

can be designed by performing simple calculations for

a first iteration. All designs should be prototyped and

tested prior to production. Table 1 provides a list of

current, allowing 0A at V = 0.5V to the full current limit

at V = 1.5V. The maximum load current is available

_______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

Table 1. Component Selection

(V)

(kΩ)

COMP

(pF)

OUT

OSC

COMP

COMP2

(pF)

OUT(MAX)

(mA)

(V)

L (µH)

(µF)

OUT

(Hz)

MAX1790

10 (Sumida

CDRH5D18-100NC)

33 tantalum (AVX

TPSD336020R0200)

3.3

640k

1.2M

640k

1.2M

120

180

1200

650

820

390

250

800

5.4 (Sumida

CDRH5D18-5R4NC)

33 tantalum (AVX

TPSD336020R0200)

3.3

5.4 (Sumida

CDRH5D18-5R4NC)

47 tantalum

(6TPA47M)

2.7 (Sumida

CDRH4D18-2R7)

47 tantalum

(6TPA47M)

3.3

MAX8715

3 x 3.3 ceramic

(Taiyo Yuden

LMK325BJ335MD)

6.8 (Sumida

CLQ4D10-6R8)

3.3

1.2M

750

150

as well as maximum and minimum input voltages.

Begin by selecting an inductor value. Once L is known,

choose the diode and capacitors.

Table 2. Component Suppliers

SUPPLIER

Inductors

PHONE

FAX

Inductor Selection

The minimum inductance value, peak current rating, and

series resistance are factors to consider when selecting

the inductor. These factors influence the converter’s effi-

ciency, maximum output load capability, transient-

response time, and output voltage ripple. Physical size

and cost are also important factors to be considered.

Coilcraft

Coiltronics

Sumida USA

TOKO

847-639-6400

561-241-7876

847-956-0666

847-297-0070

847-639-1469

561-241-9339

847-956-0702

847-699-1194

Capacitors

AVX

The maximum output current, input voltage, output volt-

age, and switching frequency determine the inductor

value. Very high inductance values minimize the current

ripple and therefore reduce the peak current, which

decreases core losses in the inductor and I²R losses in

the entire power path. However, large inductor values

also require more energy storage and more turns of wire,

which increase physical size and can increase I²R loss-

es in the inductor. Low inductance values decrease the

physical size but increase the current ripple and peak

current. Finding the best inductor involves choosing the

best compromise between circuit efficiency, inductor

size, and cost.

803-946-0690

408-986-0424

619-661-6835

408-573-4150

803-626-3123

408-986-1442

619-661-1055

408-573-4159

Kemet

Sanyo

Taiyo Yuden

Diodes

Central

Semiconductor

516-435-1110

310-322-3331

516-435-1824

310-322-3332

International

Rectifier

Motorola

Nihon

602-303-5454

847-843-7500

516-543-7100

602-994-6430

847-843-2798

516-864-7630

The equations used here include a constant LIR, which

is the ratio of the inductor peak-to-peak ripple current to

the average DC inductor current at the full load current.

The best trade-off between inductor size and circuit

efficiency for step-up regulators generally has an LIR

between 0.3 and 0.5. However, depending on the AC

characteristics of the inductor core material and the

Zetex

components for a range of standard applications. Table

2 lists component suppliers.

External component value choice is primarily dictated

by the output voltage and the maximum load current,

10 ______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

ratio of inductor resistance to other power path resis-

3.3V

9V − 3.3V

0.15A ×1.2MHz 0.5

0.85

⎛

⎞ ⎛

⎞⎛

⎟⎜

⎠⎝

⎞

tances, the best LIR can shift up or down. If the induc-

tor resistance is relatively high, more ripple can be

accepted to reduce the number of turns required and

increase the wire diameter. If the inductor resistance is

relatively low, increasing inductance to lower the peak

current can decrease losses throughout the power

path. If extremely thin high-resistance inductors are

used, as is common for LCD-panel applications, the

best LIR can increase to between 0.5 and 1.0.

L =

≈ 6.8μH

⎜

⎝

⎟ ⎜

⎠ ⎝

⎟

⎠

Using the circuit’s minimum input voltage (3V) and esti-

mating efficiency of 80% at that operating point:

0.15A × 9V

3V × 0.8

≈ 0.6A

IN(DC,MAX)

The ripple current and the peak current are:

Once a physical inductor is chosen, higher and lower

values of the inductor should be evaluated for efficiency

improvements in typical operating regions.

3V × (9V − 3V)

6.8μH× 9V ×1.2MHz

≈ 0.25A

RIPPLE

Calculate the approximate inductor value using the typ-

ical input voltage (V ), the maximum output current

0.25A

), the expected efficiency (η

) taken from

MAIN(MAX)

TYP

= 0.6A +

≈ 0.725A

PEAK

an appropriate curve in the Typical Operating

Characteristics, and an estimate of LIR based on the

above discussion:

Diode Selection

The output diode should be rated to handle the output

voltage and the peak switch current. Make sure that the

diode’s peak current rating is at least I

breakdown voltage exceeds V

recommended.

⎛

⎞

⎛

⎞

− V

× f

⎛

TYP

⎝ LIR ⎠

⎞

MAIN

L =

⎜

⎟

⎜

⎟

⎜

⎟

and that its

⎝

⎠

MAIN

MAIN(MAX) OSC

⎝

⎠

. Schottky diodes are

OUT

Choose an available inductor value from an appropriate

inductor family. Calculate the maximum DC input cur-

Input and Output Capacitor Selection

Low-ESR capacitors are recommended for input

bypassing and output filtering. Low-ESR tantalum

capacitors are a good compromise between cost and

performance. Ceramic capacitors are also a good

choice. Avoid standard aluminum electrolytic capaci-

tors. A simple equation to estimate input and output-

capacitor values for a given voltage ripple is as follows:

rent at the minimum input voltage V

using con-

IN(MIN)

servation of energy and the expected efficiency at that

operating point (η ) taken from an appropriate curve

MIN

in the Typical Operating Characteristics:

× V

MAIN(MAX)

MAIN

IN(DC,MAX)

× η

MIN

IN(MIN)

Calculate the ripple current at that operating point and

the peak current required for the inductor:

⎛

⎞

0.5 × L ×

⎝

⎠

C ≥

× (V

− V

)

IN(MIN)

MAIN

IN(MIN)

× V

OUT

RIPPLE

L × V

× f

MAIN OSC

where V

is the peak-to-peak ripple voltage on the

RIPPLE

capacitor.

RIPPLE

= I

PEAK

IN(DC,MAX)

Output Voltage

The inductor’s saturation current rating and the

MAX1790/MAX8715s’ LX current limit (I ) should

The MAX1790/MAX8715 operate with an adjustable

LIM

output from V to 13V. Connect a resistor voltage-

exceed I

and the inductor’s DC current rating should

PEAK

divider to FB (see the Typical Operating Circuit) from

exceed I

. For good efficiency, choose an

IN(DC,MAX)

the output to GND. Select the resistor values as follows:

inductor with less than 0.1Ω series resistance.

⎛

⎞

Considering the application circuit in Figure 4, the maxi-

OUT

R1= R2

− 1

⎟

⎜

mum load current (I

) is 150mA with a 9V output

MAIN(MAX)

⎝

⎠

and a typical input voltage of 3.3V. Choosing an LIR of 0.5

and estimating efficiency of 85% at this operating point:

where V , the boost-regulator feedback set point, is

1.24V. Since the input bias current into FB is typically 0,

______________________________________________________________________________________ 11

Low-Noise Step-Up DC-DC Converters

R2 can have a value up to 100kΩ without sacrificing

accuracy. Connect the resistor-divider as close to the IC

as possible.

2.6V TO 5.5V

10μF

10V

Loop Compensation

The voltage feedback loop needs proper compensation

to prevent excessive output ripple and poor efficiency

caused by instability. This is done by connecting a resis-

L1A

5.3μH

10μF

OUT

3.3V

tor (R

) and capacitor (C

) in series from

COMP

SHDN

COMP to GND, and another capacitor (C

COMP to GND. R

) from

COMP2

is chosen to set the high-fre-

COMP

L1B

5.3μH

OUT

MAX1790

quency integrator gain for fast transient response, while

is chosen to set the integrator zero to maintain

22μF

20V

COMP

FREQ

loop stability. The second capacitor, C

, is chosen

COMP2

GND

to cancel the zero introduced by output-capacitance

ESR. For optimal performance, choose the components

using the following equations:

1MΩ

0.027μF

≅ (200Ω / A ) x V

x C

/ L (MAX1790)

COMP

OUT

605kΩ

≅ (274Ω / A) x V x V

x C

/ (L x I

)

COMP

OUT

COMP2

56pF

(MAX8715)

COMP

22kΩ

-3

≅ (0.4 x 10 A/Ω) x L / V

(MAX1790)

(MAX8715)

COMP

330pF

-3

≅ (0.36 x 10 A/Ω) x L / V

L1 = CTX8-1P

= TPSD226025R0200

OUT

≅ (0.005 A /Ω) x R

x L / V

ESR OUT

COMP2

(MAX1790)

Figure 3. MAX1790 in a SEPIC Configuration

/ (V V

)

≅ (0.0036 A/Ω) x R

x L x I

COMP2

(MAX8715)

ESR

OUT

= maximum output current during power-up stage

= minimum input voltage

OUT

For the ceramic output capacitor, where ESR is small,

is optional. Table 1 shows experimentally verified

COMP2

The load must wait for the soft-start cycle to finish

before drawing a significant amount of load current.

The duration after which the load can begin to draw

maximum load current is:

external component values for several applications.

The best gauge of correct loop compensation is by

inspecting the transient response of the MAX1790/

MAX8715. Adjust R

obtain optimal transient performance.

and C

as necessary to

COMP

= 6.77 x 10 C

MAX

Soft-Start Capacitor

The soft-start capacitor should be large enough that it

does not reach final value before the output has

Application Circuits

1-Cell to 3.3V SEPIC Power Supply

Figure 3 shows the MAX1790 in a single-ended primary

inductance converter (SEPIC) topology. This topology is

useful when the input voltage can be either higher or

lower than the output voltage, such as when converting

a single lithium-ion (Li+) cell to a 3.3V output. L1A and

L1B are two windings on a single inductor. The coupling

capacitor between these two windings must be a low-

ESR type to achieve maximum efficiency, and must also

be able to handle high ripple currents. Ceramic capaci-

tors are best for this application. The circuit in Figure 3

provides 400mA output current at 3.3V output when

operating with an input voltage from +2.6V to +5.5V.

reached regulation. Calculate C to be:

− V

OUT

⎛

⎞

V_OUT

−6

21 × 10

× C

OUT

⎜

⎟

− I

OUT

⎝

⎠

INRUSH

OUT

where:

= total output capacitance including any bypass

OUT

capacitor on the output bus

OUT

= maximum output voltage

= peak inrush current allowed

INRUSH

12 ______________________________________________________________________________________

Low-Noise Step-Up DC-DC Converters

0.1μF

-9V

10mA

+26V

5mA

3.3μF

1μF

150mA

3.0V TO 3.6V

0.47μF

274kΩ

MAX1790

MAX8715

44.2kΩ

FREQ

GND

SHDN

COMP

150kΩ (MAX1790)

82kΩ (MAX8715)

27nF

C1, C2, C3, C4: TAIYO YUDEN LMK325BJ335MD (3.3μF, 10V)

D1: ZETEX ZHCS1000 (20V, 1A, SCHOTTKY) OR MOTOROLA MBRM120ET3

D2, D3, D4: ZETEX BAT54S (30V, 200mA, SCHOTTKY)

18pF (MAX1790)

10pF (MAX8715)

470pF (MAX1790)

750pF (MAX8715)

L1: SUMIDA CLQ4D10-6R8 (6.8μH, 0.8A) OR SUMITOMO CXLM120-6R8

Figure 4. Multiple-Output, Low-Profile (1.2mm max) TFT-LCD Power Supply

AMLCD Application

Figure 4 shows a power supply for active matrix (TFT-

LCD) flat-panel displays. Output-voltage transient per-

formance is a function of the load characteristic. Add or

remove output capacitance (and recalculate compen-

sation-network component values) as necessary to

meet transient performance. Regulation performance

for secondary outputs (V2 and V3) depends on the load

characteristics of all three outputs.

ulation, high efficiency, and stability. It is strongly recom-

mended that the evaluation kit PC board layouts be fol-

lowed as closely as possible. Place power components

as close together as possible, keeping their traces short,

direct, and wide. Avoid interconnecting the ground pins

of the power components using vias through an internal

ground plane. Instead, keep the power components

close together and route them in a star ground configura-

tion using component-side copper, then connect the star

ground to internal ground using multiple vias.

Layout Procedure

Good PC board layout and routing are required in high-

frequency switching power supplies to achieve good reg-

Chip Information

TRANSISTOR COUNT: 1012

______________________________________________________________________________________ 13

Low-Noise Step-Up DC-DC Converters

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,

go to www.maxim-ic.com/packages.)

4X S

MILLIMETERS

INCHES

DIM MIN

MAX

MIN

0.043

0.006

0.037

0.014

0.007

0.120

1.10

0.15

0.95

0.36

0.18

3.05

0.002

0.030

0.010

0.005

0.116

0.05

0.75

0.25

0.13

2.95

Ø0.50 0.1

0.0256 BSC

0.65 BSC

0.6 0.1

0.116

0.188

0.016

0∞

0.120

2.95

4.78

0.41

0∞

3.05

5.03

0.66

6∞

0.198

0.026

6∞

0.6 0.1

0.0207 BSC

0.5250 BSC

BOTTOM VIEW

TOP VIEW

SIDE VIEW

FRONT VIEW

PROPRIETARY INFORMATION

TITLE:

PACKAGE OUTLINE, 8L uMAX/uSOP

APPROVAL

DOCUMENT CONTROL NO.

REV.

21-0036

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Printed USA

is a registered trademark of Maxim Integrated Products, Inc.

MAX1790EUA相关文章

配单直通车

深圳市中利达电子科技有限公司服务专线: 0755-83200645/13686833545 在线联系:

QQ：1902134819 复制

QQ：2881689472 复制

柒号芯城电子商务（深圳）有限公司服务专线: 0755-83209937 在线联系:

QQ：2881677436 复制

QQ：2881620402 复制

首天国际（深圳）科技有限公司服务专线: 0755-82807802/82807803 在线联系:

QQ：528164397 复制

QQ：1318502189 复制

深圳市芯福林电子有限公司服务专线: 13418564337 在线联系:

QQ：2881495808 复制

QQ：308365177 复制

北京元坤伟业科技有限公司服务专线: 010-62104931621064316210489162104791 在线联系:

QQ：857273081 复制

QQ：1594462451 复制

MAX1790EUA产品参数

型号:	MAX1790EUA
是否无铅：	含铅
是否Rohs认证：	不符合
生命周期：	Active
零件包装代码：	TSSOP
包装说明：	TSSOP,
针数：	8
Reach Compliance Code：	unknown
风险等级：	5.21
模拟集成电路 - 其他类型：	SWITCHING REGULATOR
控制模式：	CURRENT-MODE
控制技术：	PULSE WIDTH MODULATION
最大输入电压：	5.5 V
最小输入电压：	2.6 V
标称输入电压：	3 V
JESD-30 代码：	S-PDSO-G8
JESD-609代码：	e0
长度：	3 mm
湿度敏感等级：	1
功能数量：	1
端子数量：	8
最高工作温度：	85 °C
最低工作温度：	-40 °C
最大输出电流：	1.2 A
封装主体材料：	PLASTIC/EPOXY
封装代码：	TSSOP
封装形状：	SQUARE
封装形式：	SMALL OUTLINE, THIN PROFILE, SHRINK PITCH
峰值回流温度（摄氏度）：	240
座面最大高度：	1.1 mm
表面贴装：	YES
切换器配置：	BOOST
最大切换频率：	1500 kHz
温度等级：	INDUSTRIAL
端子面层：	TIN LEAD
端子形式：	GULL WING
端子节距：	0.65 mm
端子位置：	DUAL
处于峰值回流温度下的最长时间：	20
宽度：	3 mm
Base Number Matches：	1

电子百科

产品导航

产品型号MAX1790EUA的概述

产品型号MAX1790EUA的Datasheet PDF文件预览

MAX1790EUA相关产品

MAX1790EUA相关文章

IC37:专业IC行业平台