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Power Up/Down Time (ms) Options
Power Up/Down Time (ms) Options
It is possible to select the V
COM
ramp up/down time from GND level to a common voltage level orvice-versa by choosing a V
COM
capacitor value and time by choosing one of the available checkboxes. A4.7 μF V
COM
capacitor is chosen as the default setting (this capacitor is also mounted on the EVM).
The 4.7 μF V
COM
capacitor is the recommended value for operating the EVM. This configuration is therecommended power-on sequence discussed in the product data sheet .
To select a different V
COM
value, choose the appropriate value from the V
COM
capacitor drop-down menu.Be sure to change the capacitor on the EVM to the same value (1.0 μF, 2.2 μF or 10 μF).
The combination of PTM[1:0] and RES[4:0] determines the V
COM
ramp up/down time, as described inTable 3-2 and Table 3-3 .
To set the ramp up or down time without directly accessing the registers, users can select a V
COMcapacitor value and time in the group box. The ramp up waveform with the default setting is shown inFigure 3-5 , and the ramp down waveform in Figure 3-6 , as references.
Table 3-2. PCM3793A/94A Resistor 125(7dh)RES[4:0]: Resistor Value Control
RES [4:0] V
COM
Resistor Value
10000 60 k
11000 24 k
11100 12 k
11110 6 k
Others Reserved
Table 3-3. PCM3793A/94A Resistor 125(7dh) PMT[1:0]: Power Up/Down Time Control andRegister Direct Access
V
COM
Capacitor Power-Up Time Power-Down Time Register Direct[μF] RES[4:0] PTM[1:0] [ms] [ms] Access
10 11110 00 450 750 0x7D1E
11100 11 900 1500 0x7D7C
11000 Do not set
10000 Do not set
4.7 11110 01 250 400 0x7D3E
11100 00 450 750 0x7D1C (default)
11000 11 900 1500 0x7D78
10000 Do not set
2.2 11110 10 100 300 0x7D5E
11100 01 250 400 0x7D3C
11000 00 450 750 0x7D18
10000 11 900 1500 0x7D70
1.0 11110 Do not set
11100 10 100 300 0x7D5C
11000 01 250 400 0x7D38
10000 00 450 750 0x7D10
SBAU127 – July 2007 Set-Up Guide 25Submit Documentation Feedback