ADM1067ASU datasheet(18/32 Pages) AD

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ADM1067

Rev. B | Page 18 of 32

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

ADM1067ASU Datasheet(PDF) 18 Page - Analog Devices