SS8017TR SSC [Silicon Standard Corp.], SS8017TR Datasheet - Page 6

• Manufacturer Part Number: SS8017TR
• Description: Two Remote Temperature Sensors with SMBus Serial Interface and System Reset
• Manufacturer: SSC [Silicon Standard Corp.]

Rev.2.01 6/06/2003
Block Diagram
Detailed Description
The SS8017 consists of two temperature sensors, one
on-chip temperature sensor and includes a system-reset
function.
The temperature sensor is designed to work in con-
junction with an external micro-controller (µC) or other
intelligence in thermostatic, process-control, or moni-
toring applications. The µC is typically a powerman-
agement or keyboard controller, generating SMBus
serial commands by "bit-banging" general-purpose in-
put -output (GPIO) pins or via a dedicated SMBus in-
terface block.
Essentially a 12-bit serial analog-to-digital converter
(ADC) with a sophisticated front end, the SS8017 con-
tains a switched current source, a multiplexer, an ADC,
an SMBus interface, a reset circuit and associated
control logic (see block diagram above).
Temperature data from the ADC is loaded into two data
registers, where it is automatically compared with data
previously stored in four over/under-temperature alarm
registers.
DXP2
DXP1
DXP1
DXN
DXN
V
V
INTERNAL GROUND
INTERNAL GROUND
CC
CC
V
CC
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+
+
+
+
MUX
MUX
CONTROL
CONTROL
LOGIC
LOGIC
+
+
ADC and Multiplexer
The ADC is an averaging type that integrates over a
60ms period (each channel, typical).
The multiplexer automatically steers bias currents
through two remote diodes, measures their forward
voltages, and computes their temperatures. All chan-
nels are converted automatically once the conversion
process has started, either in free-running or sin-
gle-shot mode. If one of the two channels is not used,
the device still performs all measurements, and the
user can simply ignore the results of the unused chan-
nel. If the remote diode channel is unused, tie DXPx to
DXN rather than leaving the pins open.
The DXN input is internally connected to the ground
node inside the chip to set up the analog to digital (A/D)
inputs for a differential measurement. The worst-case
DXP-DXN differential input voltage range is 0.25V to
0.95V.
Excess resistance in series with the remote diode
causes about +1/2°C error per ohm. Likewise, 200µV
of offset voltage forced on DXP -DXN causes about 1°C
error.
ADC
ADC
THERMAL SHUTDOWN
THERMAL SHUTDOWN
REGISTERS
REGISTERS
LOGIC
LOGIC
SMBUS
SMBUS
CIRCUIT
CIRCUIT
RESET
RESET
RESET
RESET
SS8017
TH_SHUT
TH_SHUT
SMBCLK
SMBCLK
SMBDATA
SMBDATA
ALERT
ALERT
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