ADM1022ARQ-REEL ON Semiconductor, ADM1022ARQ-REEL Datasheet - Page 9

• Manufacturer Part Number: ADM1022ARQ-REEL
• Description: IC SENSOR TEMP/DET 3/5.5V 16QSOP
• Manufacturer: ON Semiconductor
• Type: Temperature Sensorr

Specifications of ADM1022ARQ-REEL

• Rohs Status: RoHS non-compliant
• Input Type: Logic
• Output Type: Analog
• Interface: Serial
• Current - Supply: 2.6mA
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP

TEMPERATURE MEASUREMENT SYSTEM
Internal Temperature Measurement
The ADM1022 contains an on-chip bandgap temperature sen-
sor. The on-chip ADC performs conversions on the output of
this sensor and outputs the temperature data in 8-bit twos comple-
ment format. The format of the temperature data is shown in
Table II.
External Temperature Measurement
The ADM1022 can measure the temperature of two external
diode sensors or diode-connected transistors, connected to Pins
9 and 10 or 11 and 12.
Pins 9 and 10 are a dedicated temperature input channel. The
default function of Pins 11 and 12 is the THERM input/output
and a general purpose logic input (GPI), but they can be config-
ured to measure a diode sensor by setting Bit 7 of the Configu-
ration Register to 1.
The forward voltage of a diode or diode-connected transistor,
operated at a constant current, exhibits a negative temperature
coefficient of about –2 mV/°C. Unfortunately, the absolute value
SDA
SCL
SDA
SCL
START BY
START BY
MASTER
MASTER
SDA
SCL
START BY
MASTER
1
0
1
0
1
0
1
1
1
SERIAL BUS ADDRESS BYTE
SERIAL BUS ADDRESS BYTE
0
0
SERIAL BUS ADDRESS BYTE
0
1
1
FRAME 1
FRAME 1
1
FRAME 1
1
1
1
SDA (CONTINUED)
SCL (CONTINUED)
A1
A1
A1
A0
A0
A0
R/W
R/W
ADM1022
ADM1022
ACK. BY
ACK. BY
R/W
ADM1022
ACK. BY
9
9
D7
9
1
D7
D7
1
1
of V
tion is required to null this out, so the technique is unsuitable
for mass-production.
The technique used in the ADM1022 is to measure the change
in V
This is given by:
where:
K is Boltzmann’s constant
q is charge on the carrier
T is absolute temperature in Kelvins
N is ratio of the two currents
Figure 12 shows the input signal conditioning used to mea-
sure the output of an external temperature sensor. This figure
shows the external sensor as a substrate transistor, provided
for temperature monitoring on some microprocessors, but it
could equally well be a discrete transistor.
D7
D6
1
BE
D6
BE
D6
, varies from device to device, and individual calibra-
when the device is operated at two different currents.
D6
D5
ADDRESS POINTER REGISTER BYTE
D5
D5
ADDRESS POINTER REGISTER BYTE
DATA BYTE FROM ADM1022
D5
D4
DATA BYTE
D4
D4
FRAME 3
FRAME 2
FRAME 2
D4
D3
D3
FRAME 2
D3
∆V
D3
D2
BE
D2
D2
= KT/q × ln(N)
D2
D1
D1
D1
D1
D0
D0
D0
ADM1022
ACK. BY
BY MASTER
ADM1022
NO ACK.
D0
ACK. BY
9
9
ADM1022
ACK. BY
9
ADM1022
9
STOP BY
MASTER
STOP BY
MASTER
STOP BY
MASTER