LTC2991C 查看數據表（PDF） - Linear Technology

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LTC2991C

Octal I2C Voltage, Current, and Temperature Monitor

Linear Technology 

LTC2991

OPERATION

The LTC2991 monitors voltage, current, internal and remote

temperatures. It can be configured through an I2C inter-

face to measure many combinations of these parameters.

Single or repeated measurements can be configured.

Remote temperature measurements use transistors as

temperature sensors, allowing the remote sensor to be a

discrete NPN (ex. MMBT3904) or an embedded PNP device

in a microprocessor or FPGA. The internal ADC reference

minimizes the number of support components required.

The Functional Diagram displays the main functional com-

ponents of the device. The input signals are selected with an

input mux, controlled by the control logic block. The control

logic block uses the mode bits in the control registers to

manage the sequence and types of data acquisition. The

control logic block also controls the current sources during

remote temperature acquisition. The order of acquisitions

is fixed: V1, V2, V3, V4, V5, V6, V7, V8, TINTERNAL then

VCC. The ADC performs the necessary conversion(s) and

supplies the data to the control logic for routing to the ap-

propriate data register. The I2C interface supplies access

to control, status and data registers. The ADR2, ADR1 and

ADR0 pins select one of eight possible I2C addresses (see

Table 1). The UVLO inhibits I2C communication below the

specified threshold. During an undervoltage condition, the

part is in a reset state, and the data and control registers

are placed in the default state of 00h.

Remote diode measurements are conducted using multiple

ADC conversions and source currents to compensate for

sensor series resistance. The V2, V4, V6 or V8 terminals of

the LTC2991 are terminated with a diode if that channel is

configured for temperature measurements. It is acceptable

to ground these pins, but increased noise may result on

the temperature measurements. The LTC2991 is calibrated

to yield the correct temperature for a remote diode with an

ideality factor of 1.004. See the Applications Information

section for compensation of sensor ideality factors other

than the factory calibrated value of 1.004.

The LTC2991 communicates through an I2C serial in-

terface. The serial interface provides access to control,

status and data registers. I2C defines a 2-wire open-drain

interface supporting multiple slave devices and masters

on a single bus. The LTC2991 supports 100kbit/s in the

standard mode and up to 400kbit/s in fast mode. The

eight physical addresses supported are listed in Table 1.

The I2C interface is used to trigger single conversions, or

start repeated conversions by writing to a dedicated trig-

ger register. The data registers contain a destructive read

status bit (data valid), which is used in repeated mode to

determine if the registers contents have been previously

read. This bit is set when the register is updated with new

data, and cleared when read.

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For more information www.linear.com/LTC2991

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