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
@Power_Down_0
;; Set Control Registers RF and MB is 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
VDD
VDD
VDD
SNAD02C
VDD
SNC520
AVDD
REF
VDD
Battery:
1.5Vx3
0.1uF
START
CLK
DIO
P22
P21
P20
VSS
AVSS
VSS
CH[7]
VDD
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
24
SONIX [ SONIX TECHNOLOGY COMPANY ]
