lm95221cimm-eng National Semiconductor Corporation, lm95221cimm-eng Datasheet - Page 7

• Manufacturer Part Number: lm95221cimm-eng
• Description: Dual Remote Diode Digital Temperature Sensor With Smbus Interface
• Manufacturer: National Semiconductor Corporation

Typical Performance Characteristics
1.0 Functional Description
The LM95221 is a digital sensor that can sense the tempera-
ture of 3 thermal zones using a sigma-delta analog-to-digital
converter. It can measure its local die temperature and the
temperature of two diode connected MMBT3904 transistors
using a ∆V
interface, of the LM95221, is compatible with SMBus 2.0 and
I2C. Please see the SMBus 2.0 specification for a detailed
description of the differences between the I2C bus and
SMBus.
The temperature conversion rate is programmable to allow
the user to optimize the current consumption of the LM95221
to the system requirements. The LM95221 can be placed in
shutdown to minimize power consumption when tempera-
ture data is not required. While in shutdown, a 1-shot con-
version mode allows system control of the conversion rate
for ultimate flexibility.
The remote diode temperature resolution is eleven bits and
is programmable to 11-bits unsigned or 10-bits plus sign.
The least-significant-bit (LSb) weight for both resolutions is
0.125˚C. The unsigned resolution allows the remote diodes
Thermal Diode Capacitor or PCB Leakage Current Effect
Conversion Rate Effect on Average Power Supply
be
Remote Diode Temperature Reading
temperature sensing method. The 2-wire serial
Current
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to sense temperatures above 127˚C. Local temperature
resolution is not programmable and is always 9-bits plus sign
and has a 0.25˚C LSb.
The LM95221 remote diode temperature accuracy will be
trimmed for the thermal diode of a Prescott processor and
the accuracy will be guaranteed only when using this diode.
Diode fault detection circuitry in the LM95221 can detect the
presence of a remote diode: whether D+ is shorted to V
D- or ground, or whether D+ is floating.
The LM95221 register set has an 8-bit data structure and
includes:
1. Most-Significant-Byte (MSB) Local Temperature Regis-
2. Least-Significant-Byte (LSB) Local Temperature Regis-
3. MSB Remote Temperature 1 Register
4. LSB Remote Temperature 1 Register
5. MSB Remote Temperature 2 Register
6. LSB Remote Temperature 2 Register
Remote Temperature Reading Sensitivity to Thermal
ter
ter
Diode Filter Capacitance
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