High Efficiency Charge Pump White LED Driver
A8435
ELECTRICAL CHARACTERISTICS1
VIN = VEN1 = VEN2 = 3.6 V, C1 = C2 = 1 μF, TA = –40 to 85°C, typical values at TA = 25°C (unless otherwise noted)
Characteristics
Symbol
VIN
Test Conditions
Min.
2.7
2.25
–
Typ.
–
Max. Units
Input Voltage Range
5.5
2.60
–
V
Undervoltage Lockout Threshold
UVLO Hysteresis Window
VUVLO
VIN falling, VUVLOHYS = 35 mV
2.45
35
V
VUVLOHYS
mV
mA
μA
ms
V
Switching, TA = 25°C
–
2.8
0.1
2
4
Quiescent Current
IQ
EN1 = EN2 = GND, TA = 25°C
–
1
Soft-Start Completion Time
ISET Bias Voltage
tSS
–
–
VISETBIAS
VISETLKG
IISET
0.56
–
0.6
0.01
–
0.64
1
ISET Leakage in Shutdown
ISET Current Range
μA
μA
A/A
A/A
A/A
40
190
105
51
140
245
137
69
EN1 = EN2 = VIN
219
121
60
IISET = 60 μA,
EN1 = VIN, EN2 = GND
EN1 = GND, EN2 = VIN
CTRL = open or HIGH
ISET to LEDx Current Ratio
ILEDx/IISET
I
ISET = 60 μA,
Full brightness
–
200
–
A/A
CTRL = LOW
ILED Accuracy
LED Current Matching2
EILED
ΔILED
VLED
EN1 = EN2 = VIN, RSET = 4.3 kΩ
VIN =3.6 V, ILED = 30 mA per LED
EN1 = EN2 = VIN
–
–
–
–
–
–
–
–
–
±0.9
±0.5
150
1.1
3.6
100
60
–
–
–
–
–
–
–
1
–
%
%
Regulation Voltage at LEDx (1.5×)
mV
Ω
1× mode: [(VIN – VOUT)/IOUT
]
Open Loop Output Resistance3
ROUT
1.5× mode: [(1.5 × VIN – VOUT)/IOUT
]
Ω
1× to 1.5× Mode Transition Voltage at LEDx
Transition to Dropout Voltage Difference4
LED Leakage in Shutdown
VTrans
VLEDx Falling
mV
mV
μA
MHz
ΔVdr
Measured as VTrans – VDropout
VLEDLKG EN1 = EN2 = GND, VIN = 5.5 V, TA = 25°C
fosc
0.01
1
Oscillator Frequency
Open circuit at any LED that is programmed to be
in the ON state
Output Overvoltage Protection5
VOVP
–
5.74
–
V
CTRL, EN1, EN2 Input High Logic Threshold6
CTRL, EN1, EN2 Input Low Logic Threshold6
Input High Current
VIH
VIL
1.6
–
–
–
–
0.4
1
V
V
IIH
IIL
VIH = VIN
–
–
μA
μA
μs
μs
μs
ms
°C
Input Low Current
EN1 Pulse Low Time7
EN1 Pulse High Time7
Initial EN1 Pulse High Time7
Shutdown Delay7
VIL = GND
–
–
1
tLO
0.5
0.5
100
–
–
500
–
tHI
–
tHI(Init)
tSHDN
TSHDN
First EN1 pulse after shutdown
Falling edge of EN1 pulse
20°C hysteresis
–
–
2
3
Thermal-Shutdown Threshold
–
165
–
1Specifications guaranteed by design over operating temperature range, –40°C to 85°C.
2LED current matching is defined as (ILEDX – ILED(AVG))/ILED(AVG)
.
3The Open Loop Output Resistance for 1.5× mode is measured with one of the LEDx pins tied to ground or open (thus its voltage is always less
than 80 mV).
4Dropout Voltage, VDropout, is defined as the LEDx-to-GND voltage at which ILEDx drops 10% below the value of ILEDX at VLEDX = 200 mV.
5Guaranteed by design.
6EN2 is not used when CTRL is tied to ground.
7Applies only when CTRL is tied to ground. See figure 3 in Application Information section.
Allegro MicroSystems, Inc.
4
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
