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Performance Data and Typical Characteristic Curves

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be limited to less than the switching frequency divided by 2 (Fsw/2).

6. For Vout2, connect the network analyzer

’s isolation transformer from TP12 to TP10.

7. Connect the input signal measurement probe to TP12. Connect output signal measurement probe to

TP10.

8. Connect the ground leads of both probe channels to TP4.

9. On the network analyzer, measure the Bode plot data as TP10/TP12 (Out/In). The frequency sweep

must be limited to less than the switching frequency divided by 2 (Fsw/2).

10. Disconnect the isolation transformer from the Bode plot test points before making other

measurements, because the signal injection into the feedback loop may interfere with the accuracy of

other measurements.

6.3

Efficiency

To measure the efficiency of the power train on the EVM, it is important to measure the voltages at the

correct location. This is necessary because otherwise the measurements will include losses in efficiency

that are not related to the power train itself. Losses incurred by the voltage drop in the copper traces and

in the input and output connectors are not related to the efficiency of the power train, and they must not be

included in efficiency measurements.

When measuring the efficiency of Vout1, Vout2 must be disabled by the user via the Fusion GUI.

Likewise, when measuring the efficiency of Vout2, Vout1 must be disabled by the user. See the list in

Table 5 for the proper locations to measure efficiency.

Table 5. List of Test Points for Efficiency Measurements

Test Point

Node Name

Description

Comment

TP5

VIN

Measurement point for VIN +VE

Copper dot at high-side FET drain

TP23

PGND

Measurement point for VIN

–VE

Copper dot at low-side FET source

TP27

VOUT1

Measurement point for VOUT1 +VE

Copper dot at output inductor, dc side

TP23

PGND

Measurement point for VOUT1

–VE

Copper dot at low-side FET source

TP24

VIN

Measurement point for VIN +VE

Copper dot at high-side FET drain

TP25

PGND

Measurement point for VIN

–VE

Copper dot at low-side FET source

TP26

VOUT2

Measurement point for VOUT2 +VE

Copper dot at output inductor, dc side

TP25

PGND

Measurement point for VOUT2

–VE

Copper dot at low-side FET source

Input current can be measured at any point in the input wires, and output current can be measured

anywhere in the output wires of the output being measured. Using these measurement points result in

efficiency measurements that do not include losses due to the connectors and PCB traces.

6.4

Equipment Shutdown

1. Reduce the load current on both outputs to 0 A.

2. Reduce input voltage to 0 V.

3. Shut down the external fan if in use.

4. Shut down equipment.

Performance Data and Typical Characteristic Curves

Figure 5 through Figure 25 present typical performance curves for the PWR091EVM.

Using the PWR091EVM Dual-Output DC/DC Analog With PMBus Interface

SLVU638

– January 2012

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