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ADC128D818 (National Semiconductor) : Total 38 Pages

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ADC128D818
April 1, 2010
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12-Bit, 8-Channel, ADC System Monitor with Temperature
Sensor, Internal/External Reference, and I2C Interface
1.0 General Description
The ADC128D818 I2Csystem monitor is designed for max-
imum flexibility. The system monitor can be configured for
single-ended and/or pseudo-differential inputs. An on-board
temperature sensor, combined with WATCHDOG window
comparators, and an interrupt output pin, INT, allow easy
monitoring and out-of-range alarms for every channel. A high
performance internal reference is also available to provide for
a complete solution in the most difficult operating conditions.
The ADC128D818’s 12-bit delta-sigma ADC supports Stan-
dard Mode (Sm, 100 kbits/s) and Fast Mode (Fm, 400kbits/s)
I2C interfaces. The ADC128D818 includes a sequencer to
control channel conversions and stores all converted results
in independent registers for easy microprocessor retrieval.
Unused channels can be shut down independently to con-
serve power.
The ADC can use either an internal 2.56V reference or a vari-
able external reference. An analog filter is included on the
I2C digital control lines to provide improved noise immunity.
The device also includes a TIMEOUT reset function on SDA
and SCL to prevent I2C bus lock-up.
The ADC128D818 operates from +3.0 to +5.5V power supply
voltage range, –40°C to 125°C temperature range, and the
device is available in a 16-pin TSSOP package.
2.0 Applications
Communications Infrastructure
Thermal / Hardware Server Monitors
System Monitors
Industrial and Medical Systems
Electronic Test Equipment and Instrumentation
Power Supply Monitoring / Supervision
3.0 Features
12-bit Resolution Delta-Sigma ADC
Local Temperature Sensing
Configurable Single-Ended and/or Pseudo-Diff. Inputs
+2.56V Internal VREF or Variable External VREF
WATCHDOG Window Comparators with Status and Mask
Registers of All Measured Values
Independent Registers for Storing Measured Values
INT Output Notifies Microprocessor of Error Event
I2C Serial Bus Interface Compatibility
9 Selectable Addresses
TIMEOUT Reset Function to Prevent I2C Bus Lock-Up
Individual Channel Shutdown to Limit Power Consumption
Deep Shutdown Mode to Minimize Power Consumption
TSSOP 16-Lead Package
4.0 Key Specifications
■ ADC Resolution
■ Supply Voltage Range
■ Total Unadjusted Error
■ Integral Non-Linearity
■ Differential Non-Linearity
■ Operating Current
■ Deep Shutdown Current
■ Temperature Resolution
■ Temp. Accuracy (–40°C to 125°C)
■ Temp. Accuracy (–25°C to 100°C)
12-bit
+3.0V to +5.5V
–0.45/+0.2%
±1LSb
±1LSb
0.56 mA
10 µA
0.5°C/LSb
± 3°C
± 2°C
5.0 Typical Application
I2C® is a registered trademark of the Philips Corporation.
© 2010 National Semiconductor Corporation 300963
30096301
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6.0 Ordering Information
Temperature Range
–40°C TA +125°C
NS
Package
Number
Order Number Device Marking
ADC128D818CIMT1
ADC128D818CIMTX
2
ADC128D81
8CIMT
MO-153
Specified
Power
Supply
Voltage
+3.0V to
+5.5V
Note: 1-Rail transport media, 61 parts per rail
2-Tape and reel transport media, 2500 parts per reel
6.0 Connection Diagram
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7.0 Pin Descriptions
Pin
Number
Pin
Name(s)
ESD
Structure
1 VREF
2 SDA
3 SCL
4 GND
5 V+
6 INT
7-8
A0 - A1
9 - 16
IN7 - IN0
30096302
Type
Analog Input
Description
ADC external reference.
ADC128D818 allows two choices for sourcing VREF:
internal or external. If the +2.56V internal VREF is used,
leave this pin unconnected. If the external VREF is used,
source this pin with a voltage between +1.25V and V+. At
Power-On-Reset (POR), the default setting is the internal
VREF.
Bypass with the parallel combination of 1 μF (electrolytic
or tantalum) and 0.1 μF (ceramic) capacitors.
Digital I/O
Serial Bus Bidirectional Data. NMOS open-drain output.
Requires external pull-up resistor to function properly.
Digital Input
Serial Bus Clock. Requires external pull-up resistor to
function properly.
GROUND
POWER
Internally connected to all of the circuitry.
+3.0V to +5.5V power. Bypass with the parallel
combination of 1 μF (electrolytic or tantalum) and
0.1 μF (ceramic) bypass capacitors.
Digital Output
Interrupt Request. Active Low, NMOS, open-drain.
Requires external pull-up resistor to function properly.
Tri-Level Serial Address pins that allow 9 devices on a
Tri-Level Inputs single I2C bus.
Analog Inputs
The full scale range will be controlled by the internal or
external VREF. These inputs can be assigned as single-
ended and/or pseudo-differential inputs.
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8.0 Block Diagram
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30096303
9.0 Product Highlights
The maximum number of channels that can be enabled for each input mode are shown in the table below. Unusued channels may
be disabled through software.
Modes of
Operation
0
1
2
3
TABLE 1. Input Modes
Single-Ended Inputs
7
8
-
4
Pseudo-Differential
Inputs
-
-
4
2
Internal Temperature Cycle Time with Maximum
Measurement Number of Channels Enabled
(ms - typ).
1 88
- 96
1 52
1 76
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Conversion Modes
Continuous
Low Power
One-Shot
TABLE 2. Conversion Modes
Description
Enabled channels are measured continuously.
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Enabled channels are measured, then the device is automatically placed into shutdown
mode. This cycle is repeated every 728 ms.
When One-Shot Register (address 09h) is programmed while the device is in shutdown or
deep shutdown mode, the device will initiate a single conversion and comparison cycle, after
which the device returns to the respective mode it was in.
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