SH3100 Datasheet, PDF (65/80 Pages) Semtech Corporation – Supervisory IC with I2C Interface and PWM

POWER MANAGEMENT
Functional Descriptions (continued)
SH3100
DACSel(1,0)
00
01
10
11
Input
VDD
VBAK
Temperature
SNSE
DAC = 0
0.03
0.03
163
0.01
DAC = 78
1.47
1.47
85
0.49
DAC = 138
2.58
2.58
25
0.86
DAC = 203
3.78
3.78
-40
1.26
DAC =255
4.74
4.74
-92
1.58
Units
V
V
°C
V
Parameter
Symbol
Min
DAC switching frequency
DACclk
32
DAC DNL
DNL
DAC INL.
INL
Comparator switching delay
Td
DAC settling time
Tst
Minimum DAC setting
Maximum DAC setting
DAC resolution
Typ
± 0.5
±2
0.01
1.58
6.1
Max
2000
3
128
Units
kHz
LSB
LSB
μs
DACclk
V
V
mV
Temperature Measurement
During Mode 3 (Auto Fan Speed control), temperature measurements are made continuously, and it is only neces-
sary to read register 0x16 (ADCResult) to make a temperature reading at any time.
In other modes, temperature measurement needs to be manually set up by selecting the temperature input to the
ADC and initiating an ADC conversion as described in the previous section.
The contents of the ADCresult register are converted to temperature as follows:
• Temperature = (TK - ADCResult) + K * (T - 25ºC)
• TK = 163 when system clock is running from 32.768kHz crystal oscillator
• TK = 166 when system clock is running from the internal 32.768kHz oscillator (crystal not present)
K is the slope error of the temperature conversion curve and can vary between -0.1 and +0.1. This effectively means
that the temperature conversion slope can vary between 0.9ºC and 1.1ºC per code step. Factory calibration is carried
out at 25ºC to give a typical error of ± 1ºC and a maximum error of ± 2ºC at room temperature.
© 2006 Semtech Corp.
65
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