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Schematic
3.1
Enable Jumpers (JP1 and JP2)
TPS54291EVM-431 provides separate 3 pin 100-mil headers and shunts for exercising the TPS54291
Enable functions. Place the JP1 shunt in the Left Position connects EN1 to ground and turns on Output 1
and placing the JP2 shunt in the Left Position connects EN2 to ground and turns on Output 2.
3.2
Error Amplifier Outputs
The output of the TPS54291 transconductance error amplifiers (COMP1 and COMP2) are sensitive to
capacitive loading, including the typical 8-15pF capacitance added by an oscilloscope probe. No direct
measurements of these signals should be attempted without using an external buffer to prevent loading of
the control voltage.
3.3
Test Point Descriptions
Table 2. Test Point Descriptions
Test Point
Label
Use
Section
TP1
VIN
Monitor Input Voltage
3.3.1
TP2
GND
Ground for Input Voltage
3.3.1
TP3
VOUT1
Monitor VOUT1 Voltage
3.3.2
TP4
GND
Ground for VOUT1 Voltage
3.3.2
TP5
GND
Ground for VOUT1 Channel B Loop Monitoring
3.3.3
TP6
CHB
VOUT1 Channel B for Loop Monitoring
3.3.3
TP7
GND
Ground for VOUT1 Channel A Loop Monitoring
3.3.3
TP8
CHA
VOUT1 Channel B for Loop Monitoring
3.3.3
TP9
SW1
Monitor Switching Node of Channel 1
3.3.4
TP10
GND
Ground for Switch Node of Channel 1
3.3.4
TP11
IC_GND
Monitor IC Ground
3.3.5
TP12
SW2
Monitor Switching Node of Channel 2
3.3.6
TP13
GND
Ground for Switch Node of Channel 2
3.3.6
TP14
CHA
VOUT2 Channel A for Loop Monitoring
3.3.7
TP15
GND
Ground for VOUT2 Channel A Loop Monitoring
3.3.7
TP16
CHB
VOUT2 Channel B for Loop Monitoring
3.3.7
TP17
GND
Ground for VOUT2 Channel B Loop Monitoring
3.3.7
TP18
VOUT2
Monitor VOUT2 Voltage
3.3.8
TP19
GND
Ground for VOUT2 Voltage
3.3.8
3.3.1
Input Voltage Monitoring (TP1 and TP2)
TPS54291EVM-431 provides two test points for measuring the voltage applied to the module. This allows
the user to measure the actual module voltage without losses from input cables and connectors. All input
voltage measurements should be made between TP1 and TP2. To use TP1 and TP2, connect a voltmeter
positive terminal to TP1 and negative terminal to TP2.
3.3.2
Channel 1 Output Voltage Monitoring (TP3 and TP4)
TPS54291EVM-431 provides two test points for measuring the voltage generated by the module. This
allows the user to measure the actual module output voltage without losses from output cables and
connectors. All output voltage measurements should be made between TP3 and TP4. To use TP3 and
TP4, connect a voltmeter positive terminal to TP3 and negative terminal to TP4. For Output ripple
measurements, TP3 and TP4 allow a user to limit the ground loop area by using the Tip and Barrel
measurement technique shown in Figure 3. All output ripple measurements should be made using the Tip
and Barrel measurement. . Even this Tip and Barrel measurement technique increases the measured
switch edge noise. For improved output ripple measurement, measure the output ripple at the output
capacitor (C5)
5
SLVU356 – January 2010
Using the TPS54291EVM-431 A 12V Input, 3.3V 1.5A and 1.2V 2.5A
Synchronous Buck Converter
Copyright © 2010, Texas Instruments Incorporated
