cef830g Hope Microelectronics co., Ltd, cef830g Datasheet - Page 42

• Manufacturer Part Number: cef830g
• Description: Rf42/43 Ism Transmitter
• Manufacturer: Hope Microelectronics co., Ltd

7.5. Low Battery Detector
A low battery detector (LBD) with digital read-out is integrated into the chip. A digital threshold may be programmed
into the lbdt[4:0] field in "Register 1Ah. Low Battery Detector Threshold". When the digitized battery voltage
reaches this threshold an interrupt will be generated on the nIRQ pin to the microcontroller. The microcontroller will
then need to verify the interrupt by reading "Register 03h. Interrupt/Status 1" and ―Register 04h. Interrupt/Status 2,‖.
If the LBD is enabled while the chip is in SLEEP mode, it will automatically enable the RC oscillator which will
periodically turn on the LBD circuit to measure the battery voltage. The battery voltage may also be read out
through "Register 1Bh. Battery Voltage Level" at any time when the LBD is enabled. The Low Battery Detect
function is enabled by setting enlbd=1 in "Register 07h. Operating Mode and Function Control 1".
The LBD output is digitized by a 5-bit ADC. When the LBD function is enabled, enlbd = 1 in "Register 07h. Operating
Mode and Function Control 1", the battery voltage may be read at anytime by reading "Register 1Bh. Battery Voltage
Level". A Battery Voltage Threshold may be programmed to register 1Ah. When the battery voltage level drops below
the battery voltage threshold an interrupt will be generated on nIRQ pin to the microcontroller if the LBD interrupt is
enabled in ―Register 06h. Interrupt Enable 2,‖. The microcontroller will then need to verify the interrupt by reading the
interrupt status register, Addresses 03 and 04H. The LSB step size for the LBD ADC is 50 mV, with the ADC range
demonstrated in the table below. If the LBD is enabled the LBD and ADC will automatically be enabled every 1 s for
approximately 250 μs to measure the voltage which minimizes the current consumption in Sensor mode. Before an
interrupt is activated four consecutive readings are required.
Ad
1A
1B
R/W
Tel: [phone]
R/W
R
Detector Threshold
Function/Descri
Battery Voltage
Low Battery
ption
Level
BatteryVoltageV =1.7+50mV
Fax: [phone]
ADC Value
D7
0
……
29
30
31
0
1
2
D6
0
D5
0
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vbat[4]
lbdt[4]
D4
X
VDD Voltage [V]
ADCValue
vbat[3]
lbdt[3]
1.7–1.75
1.75–1.8
3.1–3.15
3.15–3.2
D3
< 1.7
……
>3.2
vbat[2]
lbdt[2]
D2
R F 4 2 / 4 3
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vbat[1]
lbdt[1]
D1
vbat[0]
lbdt[0]
D0
POR
Def.
14h
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42