SS8018TR SSC [Silicon Standard Corp.], SS8018TR Datasheet - Page 7

• Manufacturer Part Number: SS8018TR
• Manufacturer: SSC [Silicon Standard Corp.]

Rev.2.01 6/06/2003
Low-Power Standby Mode
Standby mode disables the ADC and reduces the sup-
ply-current drain to about 10µA. Enter standby mode by
forcing high to the
byte register. Software standby mode behaves such that
all data is retained in memory, and the SMB interface is
alive and listening for reads and writes.
Software standby mode is not a shutdown mode. With
activity on the SMBus, extra supply current is drawn
(see Typical Operating Characteristics). In software
standby mode, the G781 can be forced to perform A/D
conversions via the one-shot command, despite the
mand is received while a conversion is in progress, the
conversion cycle is truncated, and the data from that
conversion is not latched into either temperature reading
register. The previous data is not changed and remains
available.
Supply-current drain during the 125ms conversion pe-
riod is always about 320µA. Slowing down the conver-
sion rate reduces the average supply current (see Typi-
cal Operating Characteristics). In between conversions,
the instantaneous supply current is about 25µA due to
the current consumed by the conversion rate timer. In
standby mode, supply current drops to about 3µA. At
very low supply voltages (under the power-on-reset
threshold), the supply current is higher due to the ad-
dress pin bias currents. It can be as high as 100µA, de-
pending on ADD0 and ADD1 settings.
SMBus Digital Interface
From a software perspective, the SS8018 appears as a
set of byte-wide registers that contain temperature data,
alarm threshold values, or control bits, A standard
SMBus 2-wire serial interface is used to read tempera-
ture data and write control bits and alarm threshold data.
Each A/D channel within the device responds to the
same SMBus slave address for normal reads and writes.
The SS8018 employs four standard SMBus protocols:
Write Byte, Read Byte, Send Byte, and Receive Byte
(Figure 3). The shorter Receive Byte protocol allows
quicker transfers, provided that the correct data register
was previously selected by a Read Byte instruction. Use
caution with the shorter protocols in multi-master sys-
tems, since a second master could overwrite the com-
RUN
/STOP bit being high. If software standby com-
RUN
/STOP bit in the configuration
www.SiliconStandard.com
Table 3. Extended Temperature Data Format
mand byte without informing the first master.
The temperature data format is 11bits plus sign in
twos-complement form for remote channel, with each
data bit representing 0.125°C (Table 2, Table 3), trans-
mitted MSB first.
Table 2. Temperature Data Format
(Two’s-Complement)
+127.875
+126.375
TEMP.
-65.000
+0.125
-0.125
-1.125
-55.25
+25.5
+1.75
-25.5
(°C)
+0.5
RESOLUTION
EXTENDED
0.000°C
0.125°C
0.250°C
0.375°C
0.500°C
0.625°C
0.750°C
0.875°C
SIGN
0
0
0
0
0
0
1
1
1
1
1
DIGITAL OUTPUT
MSB
111
111
001
000
000
000
111
111
110
100
011
DATA BITS
1111
1110
1001
0001
0000
0000
1111
1110
0110
1000
1111
LSB
DATA BITS
0000 0000
0010 0000
0100 0000
0110 0000
1000 0000
1010 0000
1100 0000
1110 0000
SS8018
EXT
111
011
100
110
100
001
111
111
100
110
000
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