Texas Instruments 10A, 12V Input, 1.8V Output Synchronous Buck Converter using the TPS40192 and NexFET MOSFETs TPS40192E TPS40192EVM-525 Datenbogen
Produktcode
TPS40192EVM-525
V
VOUT
+
V
VREF
R8
)
R7
R7
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Schematic
3.1
Adjusting Output Voltage (R5)
The regulated output voltage can be adjusted within a limited range by changing the ground resistor in the
feedback resistor divider (R7). The output voltage is given by the formula
feedback resistor divider (R7). The output voltage is given by the formula
(1)
Where V
VREF
= 0.591 V and R8 = 20 k
Ω
contains common values for R7 to generate popular output voltages. TPS40192EVM-525 is stable
through these output voltages but the efficiency may suffer as the power stage is optimized for the 1.8-V
output.
output.
Table 1. Adjusting V
OUT
with R7
V
OUT
(V)
R7 (k
Ω
)
3.3
4.32
2.5
6.19
2.25
7.15
2
8.25
1.8
9.76
1.5
13
1.25
19.1
1
28.7
0.9
38.3
The values in
provide less than 1% nominal set-point error in the output voltage. If a tighter
nominal value is required, R5 can be used in parallel with R7 to obtain a wider range of resistor values
using commonly available E96 resistors.
using commonly available E96 resistors.
3.2
Adjusting Short-Circuit Protection (R9)
The TPS40192 uses a selectable current limit for short-circuit protection. The current limit is selected from
three levels by placing a resistor at R9. The TPS40192 compares the voltage drop across the high-side
FET (VDD to SW) to an internal reference voltage selected during start-up. The voltage levels are shown
in
three levels by placing a resistor at R9. The TPS40192 compares the voltage drop across the high-side
FET (VDD to SW) to an internal reference voltage selected during start-up. The voltage levels are shown
in
Table 2. Adjusting V
SCP
With R9
V
SCP(min)
(mV)
R9 (k
Ω
)
88
3.9
160
Open
228
12
The current before declaring short-circuit protection can be determined by dividing the V
SCP
by the R
DS(ON)
of the low-side FET (Q3).
3.3
Test Point Descriptions
Test Point
Label
Use
Section
TP1
Vin+
Monitor input voltage to the module
3.3.1
TP2
Vin–
Monitor input voltage to the module
3.3.1
TP3
Disable
Vin connection for disable circuit
3.3.2
TP4
Disable
Gate connection for disable circuit
3.3.2
TP5
Not Used
Not present on PCB
NA
TP6
COMP
Monitor COMP voltage and monitor power stage frequency response
3.3.3 and 3.3.5
5
SLUU395 – December 2009
Using the TPS40192EVM-525, A 12-V Input, 1.8-V Output, 10-A Synchronous
Buck Converter
Copyright © 2009, Texas Instruments Incorporated