Datasheet

www.ti.com
3.3.5 Loop Analysis (TP11, TP12, TP13, and TP14)
3.3.6 Output Voltage Monitoring (TP15 and TP16)
3.3.7 Power Good (TP17, TP18, and TP19)
3.3.8 Prebias Input (TP20)
4 Test Setup
4.1 Equipment
4.1.1 Voltage Source
4.1.2 Meters
4.1.3 Loads
Test Setup
TPS40192EVM-001 contains a 49.9- Ω series resistor in the feedback loop to allow for matched
impedance signal injection into the feedback for loop-response analysis. An isolation transformer should
be used to apply a small (30-mV or less) signal across R14 through TP12 and TP13. By monitoring the
AC injection level at TP13 and the returned AC level at TP14, the power-supply loop response can be
determined.
By moving channel A from TP12 to TP6 (COMP), the control-to-output response of the power stage (also
referred to as the power-stage transfer function) can be directly measured. See Section 3.9 for a detailed
procedure of loop-response measurements.
TPS40192EVM-001 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
connector losses. All output voltage measurements should be made between TP15 and TP16. To use
TP1 and TP2, connect a voltmeter positive terminal to TP15 and negative terminal to TP16. For output
ripple measurements, TP15 and TP16 allow a user to limit the ground loop area by using the tip and barrel
measurement technique shown in Figure 2 . All output ripple measurements should be made using this
technique.
TPS40192EVM-001 has three test points to allow the user to evaluate the TPS40192 power-good
function. TP18 provides access to the power-good output of the TPS40192. It has a 100-k Ω pullup to the
TPS40192 5-V regulator and can be used as a logic signal with no additional requirements. TP17 provides
a connection for an external power-good source for 3.3-V logic. TP17 is connected to the power-good
circuit through a 10-k Ω pullup resistor. TP19 provides a local ground access to connect a remote disable
circuit.
TPS40192EVM-001 contains a prebias injection circuit with a 100- Ω resistor and series diode to allow
testing and evaluation of the TPS40192's prebias support compatibility. Apply a voltage less than the
target output voltage to TP20. Monitoring the output voltage during start-up demonstrates the ability of the
TPS40192 to power up without drawing current from a prebiased output. D2 prevents the output voltage
from back-driving the prebias source.
The input voltage source (V
IN
) should be a 0- to 15-V variable DC source capable of 5 Adc. Connect V
IN
to
J1 as shown in Figure 1 .
A1: 0- to 5-Adc ammeter
V1: V
IN
, 0- to 15-V voltmeter
V2: V
OUT
, 0- to 5-V voltmeter
The output load (LOAD1) should be an electronic constant-current mode load capable of 0 to 10 Adc at
1.8 V.
SLVU194 – January 2007 Using the TPS40192EVM-001, A 12-V Input, 1.8-V Output, 10-A Synchronous Buck Converter 7
Submit Documentation Feedback