ADM1067
DEFAULT OUTPUT CONFIGURATION
All of the internal registers in an unprogrammed ADM1067
device from the factory are set to 0. Because of this, the PDOs are
pulled to GND by a weak (20 kΩ) on-chip pull-down resistor.
All PDOs behave as follows as the input supply to the
ADM1067 ramps up on VPn or VH:
• Input supply 0 V to 1 V. PDOs high impedance.
• Input supply 1 V to 2.7 V. PDOs pulled to GND by a weak
(20 kΩ) on-chip pull-down resistor.
• Supply > 2.7 V. Factory programmed devices continue to
pull all PDOs to GND by a weak (20 kΩ) on-chip pull-down
resistor. Programmed devices download current EEPROM
configuration data and the programmed setup is latched. PDO
then goes to the state demanded by the configuration. This
provides a known condition for the PDOs during power-up.
The internal pull-down can be overdriven with an external pull-
up of suitable value tied from the PDO pin to the required pull-up
voltage. The 20 kΩ resistor must be accounted for in calculating
a suitable value. For example, if PDOn must be pulled up to 3.3 V,
and 5 V is available as an external supply, the pull-up resistor
value is given by
3.3 V = 5 V × 20 kΩ/(RUP + 20 kΩ)
Therefore,
RUP = (100 kΩ − 66 kΩ)/3.3 V = 10 kΩ
Rev. B | Page 18 of 32