TPS53126_15 Datasheet, PDF (14/33 Pages) Texas Instruments – TPS53126 Dual Synchronous Step-down Controller For Low Voltage Power Rails

TPS53126
SLUS909B – MAY 2009 – REVISED AUGUST 2014
9 Application and Implementation
9.1 Application Information
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9.2 350 kHz Operation Application
The schematic of Figure 14 shows a typical 350 kHz application schematic. The 350 kHz switching frequency is
selected by connecting TEST2 to the GND pin. The input voltage is 4.5 V to 24 V and the output voltage is 1.8 V
for VO1 and 1.05 V for VO2.
Input Voltage
4.5V to 24V
C9
10mF
PGND
R4
R5
3.52kW ^10kW
SGND
R2
R1
10kW 13kW
65 4 3 2 1
C6
10mF
VO2
1.05V/4A
C4
22mF ´ 4
Q3
FDS8878
L2
SPM6530T
1.5mH
Q4
FDS8690
C5
0.1mF
7 EN2
8 VBST2
9 DRVH2
10 SW2
11 DRVL2
12 PGND2
PowerPAD
TPS53126
RGE
(QFN)
EN1 24
VBST1 23
DRVH1 22
SW1 21
DRVL1 20
PGND1 19
PGND
13 14 15 16 17 18
R6
3.3kW
C7
4.7mF
C8
1mF
PGND
R3
4.7kW
C2
0.1mF
Q1
FDS8878
L1
SPM6530T
1.5mH
Q2
FDS8690
C3
10mF
VO1
1.8V/4A
C1
22mF ´ 4
PGND
SGND
Figure 14. Typical Application Circuit at 350kHz Switching Frequency Selection (TEST2 Pin = GND)
9.2.1 Design Requirements
PARAMETERS
Input voltage
Output voltage
Output Current
Switching Frequency
Table 1. Design Parameters
CHANNEL 1
4.5 V to 24 V
1.8 V
4A
350 kHz
CHANNEL 2
4.5 V to 24 V
1.05 V
4A
350 kHz
9.2.2 Detailed Design Procedure
9.2.2.1 Choose Inductor
The inductance value is selected to provide approximately 30% peak to peak ripple current at maximum load.
Larger ripple current increases output ripple voltage, improve S/N ratio and contribute to stable operation.
Equation 3 can be used to calculate L1.
14
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