SNAD02C datasheet(24/27 Pages) SONIX

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SNAD02C

8-CHANNEL 10-BIT ADC

9.4. Program 4: Power-down SNAD02C and Host, and Wake-up

;; Inherit from program 1

;; Enter Power-down Mode (0)

@Set_Control_Reg #0, #1, #0, #0

;; Set Control Registers RF and MB is 0

@Power_Down_0

;;SNAD02 enters power-down Mode (0)

end

;; HOST(SNC520) enter power down

…

TRIGGER:

@OFF_START

;; SET START=1

…

@Read_Port

;; READ Trigger condition or Debounce Procedure starting from here

…

9.5. Program 5: Battery Low Detection

SNC520

SNAD02C

START

CLK

DIO

VDD

AVDD

REF

VSS

AVSS

CH[7]

VDD

0.1uF

VDD

VSS

P20

P21

P22

VDD

Battery:

1.5Vx3

An application uses three 1.5V batteries for power supply. During operation, the

power of batteries keeps consumed and the voltage of battery keeps going down.

Now, voltage lower than 3.6V is treated as “Battery Low”. The ADC and band-gap

reference circuit in SNAD02 can be utilized to detect “Battery Low”.

The voltage through channel 7 to ADC is reduced to 1/6*VDD (Figure10). Thus, when

VDD=3.6V, the voltage into ADC is around 0.6V. And bandgap is chosen for

reference voltage (approximately 1.17V within the whole operation voltage range).

The value acquired from ADC is about (0.6/1.17)*256=131. For simplification

consideration, we choose “ADC’s readout < 128” as “Battery Low” condition.

Version: 1.3

July 31, 2003

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