LTC4260 View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LTC4260

Wide Range I²C Power Monitor

Linear Technology 

LTC2945

OPERATION

The LTC2945 accurately monitors current, voltage, and

power of any supply rail from 0V to 80V. An internal linear

regulator allows the LTC2945 to operate directly from a

4V to 80V rail, or from an external supply voltage between

2.7V and 5.9V. Quiescent current is less than 0.9mA in

normal operation. Enabling shutdown mode via the I2C

interface reduces the quiescent current to below 80μA.

The LTC2945 includes a shunt regulator for operation from

supply voltages above 80V.

The onboard 12-bit analog-to-digital converter (ADC) runs

either continuously or on-demand using snapshot mode.

In the default continuous scan mode, the ADC repeatedly

measures the differential voltage between SENSE+ and

SENSE– (full-scale 102.4mV) the voltage at the SENSE+

or VDD pin (full-scale 102.4V), and the voltage at the ADIN

pin (full-scale 2.048V). The conversion results are stored

in onboard registers.

In snapshot mode, the LTC2945 performs a single mea-

surement of one selected voltage or current. Snapshot

mode is enabled by setting the snapshot mode enable bit

in the CONTROL register via the I2C interface. A status bit

in the CONTROL register monitors the ADC’s conversion;

when complete, the conversion result is stored in the cor-

responding data registers.

Onboard logic tracks the minimum and maximum values

for each ADC measurement, calculates power data by

digitally multiplying the stored current and voltage data,

and triggers a user-configurable alert by pulling the ALERT

pin low when the ADC measured value falls outside the

programmed window thresholds. All logic outputs are

stored in onboard registers. The LTC2945 includes an

I2C interface to access the onboard data registers and to

program the alert threshold and control registers. Two

three-state pins, ADR1 and ADR0, are decoded to allow

nine device addresses (see Table 1). The SDA pin is split

into SDAI (input) and SDAO (output, LTC2945) or SDAO

(output, LTC2945-1) to facilitate opto-isolation.

APPLICATIONS INFORMATION

The LTC2945 offers a compact and complete solution for

high- and low-side power monitoring. With an input com-

mon mode range of 0V to 80V and a wide input supply

operating voltage range from 2.7V to 80V, this device is

ideal for a large variety of power management applications

including automotive, industrial and telecom infrastructure.

The basic application circuit shown in Figure 1 provides

monitoring of high side current with a 0.02Ω resistor

(5.12A full-scale), input voltage (102.4V full-scale) and an

external voltage (2.048V full-scale), all using an internal

12-bit resolution ADC.

Data Converter

The LTC2945 features an onboard, 12-bit Δ∑ ADC that inher-

ently averages input noise over the measurement window.

The ADC continuously monitors three voltages in sequence:

ΔSENSE first, VDD or VSENSE+ second, and VADIN third. The

differential voltage between SENSE+ and SENSE– is moni-

tored with 25μV resolution (102.4mV full-scale) to allow

accurate measurement across very low value shunt resistors.

10

VIN

4V TO 80V

C2

0.1μF

RSNS

0.02Ω

SENSE+ SENSE–

VDD

SCL

LTC2945

INTVCC

SDAI

ADR1

SDAO

ADR0

ALERT

ADIN

GND

VOUT

3.3V

R1 R2 R3

VDD

2k 2k 2k

SCL

SDA μP

VADIN

INT

GND

2945 F01

Figure 1. Monitoring High Side Current and Voltages

Using the LTC2945

The supply voltage at VDD or SENSE+ is directly measured

with 25mV resolution (102.4V full-scale). The voltage at

the uncommitted ADIN pin is measured with 0.5mV resolu-

tion (2.048V full-scale) to allow monitoring of an arbitrary

external voltage. A 12-bit digital word corresponding to

each measured voltage is stored in two adjacent registers

2945f

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