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OUT

V 0.8V

10 W ´ 0.8

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Introduction

1.3 Modifications

These evaluation modules are designed to provide access to the features of the TPS56921. Some

modifications can be made to this module.

1.3.1 Output Voltage Setpoint

The output voltage of the EVM is set either externally using a voltage divider or internally using the

integrated I

C™ interface. The external adjustment of the output voltage is set by the resistor divider

network of R10 and R11. R10 is fixed at 10 kΩ. To change the output voltage of the EVM, it is necessary

to change the value of resistor R11. Changing the value of R11 can change the output voltage in the

range of 0.72 V to 1.48 V. The value of R11 for a specific output voltage can be calculated using

Equation 1.

(1)

The output voltage can also be set using the optional VID control using the I

C interface. The EVM is

designed so that the J3 connector is compatible with the HPA665-001 USB2ANY interface. Using that

control and USB2ANY_GUI software allows the output voltage to be programmed to any of 77 preset

voltages from 0.72 V to 1.48 V. See the TPS56921 datasheet for a complete description of the available

codes. With the software running and the cable attached, confirm the connection by clicking the "Read"

button under "Firmware Revision". The firmware revision number will be returned if the connection is good.

Set up the interface by selecting "Speed = _400kHz", "Address = _7Bits" and "Pull Ups = OFF" in the

"I2C" section. Click on "Set I2C". In the "3.3V/5.0V" section set "3.3V = ON" and "5.0V = OFF". Click on

"Set", then click on "Get Status". "GOOD" should be returned for both 3.3 V and 5.0 V. To communicate

with the TPS56921EVM-188, in the "Single-Register" section set "I2C Address = 34". In the "Register

Address" field, enter the data byte for the voltage you wish to set. Ignore the "Byte to Write" field. Click on

"Write" to send the data.

Table 3. Ideal VOUT versus Code

Code Binary VOUT Code Binary VOUT Code Binary VOUT

0 0000000 0.720 26 0011010 0.980 52 0110100 1.240

1 0000001 0.730 27 0011011 0.990 53 0110101 1.250

2 0000010 0.740 28 0011100 1.000 54 0110110 1.260

3 0000011 0.750 29 0011101 1.010 55 0110111 1.270

4 0000100 0.760 30 0011110 1.020 56 0111000 1.280

5 0000101 0.770 31 0011111 1.030 57 0111001 1.290

6 0000110 0.780 32 0100000 1.040 58 0111010 1.300

7 0000111 0.790 33 0100001 1.050 59 0111011 1.310

8 0001000 0.800 34 0100010 1.060 60 0111100 1.320

9 0001001 0.810 35 0100011 1.070 61 0111101 1.330

10 0001010 0.820 36 0100100 1.080 62 0111110 1.340

11 0001011 0.830 37 0100101 1.090 63 0111111 1.350

12 0001100 0.840 38 0100110 1.100 64 1000000 1.360

13 0001101 0.850 39 0100111 1.110 65 1000001 1.370

14 0001110 0.860 40 0101000 1.120 66 1000010 1.380

15 0001111 0.870 41 0101001 1.130 67 1000011 1.390

16 0010000 0.880 42 0101010 1.140 68 1000100 1.400

17 0010001 0.890 43 0101011 1.150 69 1000101 1.410

18 0010010 0.900 44 0101100 1.160 70 1000110 1.420

19 0010011 0.910 45 0101101 1.170 71 1000111 1.430

20 0010100 0.920 46 0101110 1.180 72 1001000 1.440

21 0010101 0.930 47 0101111 1.190 73 1001001 1.450

22 0010110 0.940 48 0110000 1.200 74 1001010 1.460

23 0010111 0.950 49 0110001 1.210 75 1001011 1.470

24 0011000 0.960 50 0110010 1.220 76 1001100 1.480

25 0011001 0.970 51 0110011 1.230 >76 >1001100 Illegal / Special

SLVU793–October 2012 TPS56921EVM-188, 9-A, SWIFT™ Regulator Evaluation Module

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