SNAD02C

8-CHANNEL 10-BIT ADC

If the internal bandgap reference is turned ON (RF=1), the reference voltage “VREF” of ADC is

from the internal bandgap reference circuit. This internal voltage reference circuit consumes

around 300

µA, and the output voltage of bandgap reference is around 1.17V typically.

If RF is turned off (RF=0), the MB is turned on (MB=1), the reference voltage is from “REF” pin.

Otherwise, the reference voltage source is comes from internal bandgap if RF=1 & MB=0.

6.8. Input Channel PAD (Channel 0~6)

VDD

VSS

ENCH[x]

to ADC

DI[x]

CH[x]

ENCH[x]

Pull-high resistor

Pull-low resistor

ENCH[x]: 1: Analog In / 0: Digital In

PH&ENCH[x]

PL&ENCH[x]

Figure-11 Circuit diagram of the Input Channel PAD

(1) If any channel is programmed to be analog input mode, then the corresponding internal

signal, ENCH[x]=1. As in Figure-11, pull-high and pull-low are disabled. And the path to

digital input is blocked. All digital reading operation of this channel will get the result “0”.

(2) If any channel is programmed to digital input mode, then the corresponding internal signal,

ENCH[x]=0. As in Figure-11, the path to ADC is removed.

(3) While in digital input mode, this input port can be configured to be floating, weak pull-up, or

pull-down by setting the control register PH and PL, where PH&PL=1 is forbidden. The

pull-up or pull-low resister are both around 500K

Ω@3v.

(4) The default status (digital/analog, pull up/down) of all the channels are un-know after power

on, so initialize each channel to define a correct state should be done after power on.

(5) Mode of each channel (ENCH[x]) can be set by command 001.

Version: 1.3

July 31, 2003

12