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SLUS786A – OCTOBER 2007 – REVISED NOVEMBER 2007
Dual-Synchronous, Step-Down Controller with Out-of-Audio™ Operation and 100-mA
LDOs for Notebook System Power
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FEATURES
Wide Input Voltage Range: 5.5 V to 28 V
Output Voltage Range: 2 V to 5.5 V
Built-in 100-mA 5-V/3.3-V LDO with Switches
Built-in 1% 2-V Reference Output
With/Without Out-of-Audio™ Mode Selectable
Light Load and PWM only Operation
Internal 1.6-ms Voltage Servo Softstart
Adaptive On-Time Control Architecture with
Four Selectable Frequency Setting
4500 ppm/°C R
DS(on)
Current Sensing
Built-In Output Discharge
Power Good Output
Built-in OVP/UVP/OCP
Thermal Shutdown (Non-latch)
QFN24 (RGE)
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DESCRIPTION
The TPS51125 is a cost effective, dual-synchronous
buck controller targeted for notebook system power
supply solutions. It provides 5-V and 3.3-V LDOs and
requires few external components. The 270-kHz
VCLK output can be used to drive an external charge
pump, generating gate drive voltage for the load
switches without reducing the main converter’s
efficiency. The TPS51125 supports high efficiency,
fast transient response and provides a combined
power-good signal. Out-of-Audio™ mode light-load
operation enables low acoustic noise at much higher
efficiency than conventional forced PWM operation.
Adaptive on-time D-CAP™ control provides
convenient and efficient operation. The part operates
with supply input voltages ranging from 5.5 V to 28 V
and supports output voltages from 2 V to 5.5 V. The
TPS51125 is available in a 24-pin QFN package and
is specified from -40°C to 85°C ambient temperature
range.
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APPLICATIONS
Notebook Computers
I/O Supplies
System Power Supplies
Typical Application Diagram
SGND
C0
0.22mF
R4
20kW
R2
20kW
R3
13kW
R6
110kW
SGND
VIN
6
RIP
2
R1
30kW
R5
110kW
SGND
3.3V/100mA
-
5
2
VF
B
4
NS
EL
3
VR
EF
2
VF
B
1
1
RIP
1
VIN
+
C5
10mF
PG
R7
100kW VREG5
C6
10mF
VIN
5.5 ~ 28V
C7
10mF
C8
10mF
C20
10mF
EN
T
7 VO2
TO
EN
T
VO1
24
8 VREG3
PGND
PGOOD
23
PGND
PGND
L2
3.3mH
VO2
3.3V/6A
+
Q3
IRF7821
C4
0.1mF
9 VBST2
R8
5.1W
10 DRVH2
TPS51125RGE
(QFN24)
VBST1
22
R9
5.1W
C3
0.1mF
Q1
IRF7821
DRVH1
21
L1
3.3mH
+
VO1
5V/6A
11 LL2
CO2
POSCAP
330mF
Q4
IRF7821
12 DRVL2
EN
0
PowerPAD
LL1
20
Q2
IRF7821
CO1
POSCAP
330mF
SE
L
DRVL1
VR
EG
5
GN
D
VIN
VC
L
K
19
VO2_GND
-
SGND
PGND
PGND
13
14
SK
IP
15
16
17
18
PGND
VREG5
-
PGND
VO1_GND
EN0
-
-
C21
10mF
R10
620kW
VREF
VO1
D0
5V/100mA
C11
100n
F
C10
100n
F
D1
D2
C13
100n
F
-
C12
100n
F
D4
15V/10mA
PGND
SGND
PGND
C14
1uF
PGND
PGND
PGND
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Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Out-of-Audio, D-CAP are trademarks of Texas Instruments.
Copyright © 2007, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
TI [ TEXAS INSTRUMENTS ]
