wm8742 Wolfson Microelectronics plc, wm8742 Datasheet - Page 16

• Manufacturer Part Number: wm8742
• Description: 24-bit 192khz Dac With Advanced Digital Filtering
• Manufacturer: Wolfson Microelectronics plc

WM8742
INTERNAL POWER ON RESET CIRCUIT
Figure 7 AVDD Power up Sequence
Table 6 Analogue POR Timing
w
Test Conditions
AVDD = 5V, AGND = 0V, T
PARAMETER
Power Supply Input Timing Information
AVDD level to POR rising
edge (AVDD rising)
AVDD level to POR falling
edge (AVDD falling)
A
The WM8742 includes two internal Power On Reset (POR) circuits which are used to reset the digital
logic into a default state after power up and to allow the analogue circuits to power-up silently.
The digital POR circuit is powered from DVDD. This circuit monitors DVDD and asserts the internal
digital reset if DVDD are below the minimum DVDD threshold which will allow the digital logic to
function.
The analogue POR circuit is powered from AVDD. The circuit monitors AVDD, tri-stating the DAC
outputs and isolating the internal reference resistor strings from AVDDL and AVDDR until there is
sufficient AVDD voltage to allow the analogue DAC stages to function correctly.
= +25
SYMBOL
V
V
o
por_hi
por_lo
C, T
A_max
= +125
Measured from AGND
Measured from AGND
o
TEST CONDITIONS
C, T
A_min
= -25
o
C, AVDD
max
= 5.5V, AVDD
MIN
min
= 4.5V
2.00
1.84
TYP
PD, Rev 4.2,August 2009
MAX
Production Data
UNIT
V
V
16