wm8215 Wolfson Microelectronics plc, wm8215 Datasheet - Page 12

• Manufacturer Part Number: wm8215
• Description: 60msps 10-bit 3-channel Ccd Digitiser
• Manufacturer: Wolfson Microelectronics plc

WM8215
w
Figure 7 Typical Power up Sequence where DVDD1 is Powered before AVDD
Figure 7 shows a typical power-up sequence where DVDD1 comes up first. First it is assumed that
DVDD1 is already up to specified operating voltage. When AVDD goes above the minimum
threshold, Vpora, there is enough voltage for the circuit to guarantee PORB is asserted low and the
chip is held in reset. In this condition, all writes to the control interface are ignored. When AVDD rises
to Vpora_on, PORB is released high and all registers are in their default state and writes to the
control interface may take place.
On power down, where DVDD1 falls first, PORB is asserted low whenever DVDD1 drops below the
minimum threshold Vpord_off.
Table 1 Typical POR Operation (typical values, not tested)
Note: It is recommended that every time power is cycled to the WM8215 a software reset is written
to the software register to ensure that the contents of the control registers are at their default values
before carrying out any other register writes.
SYMBOL
V
V
V
V
V
pora_on
pora_off
pord_on
pord_off
pora
TYP
0.6
1.2
0.6
0.7
0.6
UNIT
V
V
V
V
V
PD, Rev 4.2, February 2009
Production Data
12