Texas Instruments DRV2667, User Manual, Page: 20 / 36

FB
DRV2667
VBST
R1
R2
R4 R3
Q1
GAIN1 GAIN0
Hardware Configuration
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3.6.1 Adjusting the Boost Voltage Using Software
The boost output voltage (VBST) is programmed by two external feedback resistors R1 and R2, as shown
in the
Figure 25 . The DR2667EVM-CT includes two additional resistors, R3 and R4, which allow the
MSP430 to programmatically adjust VBST using a combination of the four resistors to produce four
different voltage levels. Refer to
Table 8 for VBST at each gain setting and the equivalent low-side
resistance.
Figure 25. Boost Voltage Programming Resistors
NOTE: Remove R3 and R4 if adjusting VBST using resistors R1 and R2.
Table 8. Boost Voltage using MSP430 GPIO Control
GAIN1 GAIN0 V
FB
Low-Side Resistance VBST
0 0 35.7 k Ω 30
0 1 19.1 k
Ω
54
1 0 12.8 k Ω 80
1 1 9.8 k Ω 105
To change the default boost voltage on the DRV2667EVM-CT using the embedded software, follow the
instructions below:
1. Enter Design & Test Modes.
2. Select Mode 30 (11110’b) using the increment mode button (“+”).
3. Select the gain and voltage using buttons B1–B4:
• B1 – 28.8 dB, 50 Vpp
• B2 – 34.8 dB, 100 Vpp
• B3 – 38.4 dB, 150 Vpp
• B4 – 40.7 dB, 200 Vpp
4. Exit Mode 30 and use the board as normal.
NOTE: the DRV2667EVM-CT will revert to the original voltage setting (150 Vpp) on power down.
3.6.2 Adjusting the Boost Voltage Using Hardware
The boost voltage is adjustable using the two GPIOs; GAIN1 and GAIN0, in code. In most applications,
however, the boost voltage is fixed so R3 and R4 are not necessary and the boost voltage can simply be
set by R1 and R2. To replace R1 and R2, first remove R3 and R4 and use
Equation 3 to calculate the
boost output voltage.
20 DRV2667 Evaluation Module SLOU323 – June 2013
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