Datasheet

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3.1 Adjusting Output Voltage (R5)
V
VOUT
+ V
VREF
R8 ) R7
R7
(1)
3.2 Adjusting Short-Circuit Protection (R9)
3.3 Test Point Descriptions
Schematic
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
Where V
VREF
= 0.591 V and R8 = 20 k Ω
Table 1 contains common values for R7 to generate popular output voltages. TPS40192EVM-001 is stable
through these output voltages but the efficiency may suffer as the power stage is optimized for the 1.8-V
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 Table 1 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.
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 Table 2 .
Table 2. Adjusting V
SCP
With R9
V
SCP(min)
(V) 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 high-side FET (Q2).
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
SLVU194 – January 2007 Using the TPS40192EVM-001, A 12-V Input, 1.8-V Output, 10-A Synchronous Buck Converter 5
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