Datasheet

VO = 0.765 1+

R 2

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Modifications

3 Modifications

These evaluation modules are designed to provide access to the features of the TPS54228. Some

modifications can be made to this module.

3.1 Output Voltage Setpoint

To change the output voltage of the EVMs, it is necessary to change the value of resistor R1. Changing

the value of R1 can change the output voltage above 0.765 V. The value of R1 for a specific output

voltage can be calculated using Equation 1.

For output voltage from 0.76 V to 7.0 V:

(1)

Table 3 lists the R1 values for some common output voltages. For higher output voltages of 1.8 V or

above, a feedforward capacitor (C4) may be required to improve phase margin. Pads for this component

(C4) are provided on the printed-circuit board. Note that the resistor values given in Table 3 are standard

values and not the exact value calculated using Equation 1.

Table 3. Output Voltages

C9. C10, C11

Output Voltage R1 R2 C4 L1 Total

(V) (kΩ) (kΩ) (pF) (µH) Capacitance

(µF)

1.0 6.81 22.1 1.5 - 2.2 22 - 68

1.05 8.25 22.1 1.5 - 2.2 22 - 68

1.2 12.7 22.1 2.2 22 - 68

1.5 21.5 22.1 2.2 22 - 68

1.8 30.1 22.1 5 - 22 3.3 22 - 68

2.5 49.9 22.1 5 - 22 3.3 22 - 68

3.3 73.2 22.1 5 - 22 3.3 22 - 68

5.0 124 22.1 5 - 22 4.7 22 - 68

6.5 165 22.1 5 - 22 4.7 22 - 68

3.2 Output Filter and Closed-Loop Response

The TPS54228 relies on the output filter characteristics to ensure stability of the control loop. The

recommended output filter components for common output voltages are given in Table 3. It may be

possible for other output filter component values to provide acceptable closed-loop characteristics. R3 and

TP4 are provided for convenience in breaking the control loop and measuring the closed-loop response.

4 Test Setup and Results

This section describes how to properly connect, set up, and use the TPS54228EVM-686. The section also

includes test results typical for the evaluation modules and efficiency, output load regulation, output line

regulation, load transient response, output voltage ripple, input voltage ripple, start-up, and switching

frequency.

SLVU452–May 2011 TPS54228EVM-686, 2-A, SWIFT™ Regulator Evaluation Module

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