SI4464 Datasheet, PDF (44/56 Pages) Silicon Laboratories – HIGH-PERFORMANCE

Si4464/63/61/60
8.3. Temperature, Battery Voltage, and Auxiliary ADC
The Si446x family contains an integrated auxiliary ADC for measuring internal battery voltage, an internal
temperature sensor, or an external component over a GPIO. The ADC utilizes a SAR architecture and achieves
11-bit resolution. The Effective Number of Bits (ENOB) is 9 bits. When measuring external components, the input
voltage range is 1 V, and the conversion rate is between 300 Hz to 2.44 kHz. The ADC value is read by first
sending the GET_ADC_READING command and enabling the inputs that are desired to be read: GPIO, battery, or
temp. The temperature sensor accuracy at 25 °C is typically ±2 °C.
Command Stream
GET_ADC_READING
Command
CMD
ADC_EN
ADC_CFG
76
00
5
4
3
2
1
0
0x14
0 TEMPERATURE_EN BATTERY_VOLTAGE_EN ADC_GPIO_EN ADC_GPIO_PIN[1:0]
UDTIME[3:0]
GPIO_ATT[3:0]
Reply Stream
GET_ADC_READING Reply
CTS
GPIO_ADC
GPIO_ADC
BATTERY_ADC
BATTERY_ADC
TEMP_ADC
TEMP_ADC
RESERVED
RESERVED
7
6
5
4
3
2
1
0
CTS[7:0]
GPIO_ADC[15:8]
GPIO_ADC[7:0]
BATTERY_ADC[15:8]
BATTERY_ADC[7:0]
TEMP_ADC[15:8]
TEMP_ADC[7:0]
Reserved
Reserved
Parameters
TEMPERATURE_EN
0 = Do not perform ADC conversion of temperature. This will read 0 value in reply TEMPERATURE.
1 = Perform ADC conversion of temperature. This results in TEMP_ADC.
Temp (°C) = TEMP_ADC[15:0] x 568/2560 – 297
BATTERY_VOLTAGE_EN
0 = Don't do ADC conversion of battery voltage, will read 0 value in reply BATTERY_ADC
1 = Do ADC conversion of battery voltage, results in BATTERY_ADC. Vbatt = 3*BATTERY_ADC/1280
ADC_GPIO_EN
0 = Don't do ADC conversion on GPIO, will read 0 value in reply
1 = Do ADC conversion of GPIO, results in GPIO_ADC. Vgpio = GPIO_ADC/GPIO_ADC_DIV where
GPIO_ADC_DIV is defined by GPIO_ATT selection.
ADC_GPIO_PIN[1:0] - Select GPIOx pin. The pin must be set as input.
0 = Measure voltage of GPIO0
1 = Measure voltage of GPIO1
2 = Measure voltage of GPIO2
3 = Measure voltage of GPIO3
UDTIME[7:4] - ADC conversion Time = SYS_CLK / 12 / 2^(UDTIME + 1). Defaults to 0xC if ADC_CFG is 0.
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Rev 1.2