TMP512 datasheet(23/62 Pages) TI2

23 / 62 page

Power Register

Current Register

Two-Wire

Interface

Voltage Register

ADC

GND

GPIO

DXP1

DXN1

DXP2

DXN2

ADC

Low-Pass Filter

MUX

DXP3

DXN3

IN+

IN-

Current

Shunt

Load

Filter C

V+

Subregulator

3.3V

Internal

Diode

Temperature

Sensor

ALERT

SDA

SCL

SMBus

Controller

3.3V Supply

TMP512

TMP513

0.1 F to 1 F

Ceramic Capacitor

10W

TMP512

TMP513

www.ti.com

SBOS491A

– JUNE 2010 – REVISED MAY 2011

COMPATIBILITY WITH TI HOT-SWAP

This architecture has good inherent noise rejection;

CONTROLLERS

however, transients that occur at or very close to the

sampling

rate

harmonics

can

cause

problems.

The TMP512/13 are designed for compatibility with

Because these signals are at 1MHz and higher, they

hot-swap controllers such the TI TPS2490. The

can be dealt with by incorporating filtering at the input

TPS2490 uses a high-side shunt with a limit at 50mV;

of the TMP512/13. The high frequency enables the

the TMP512/13 full-scale range of 40mV enables the

use of low-value series resistors on the filter for

use of the same shunt for current sensing below this

negligible

effects

measurement

accuracy.

limit. When sensing is required at (or through) the

Figure 30 shows the TMP512/13 with an additional

50mV sense point of the TPS2490, the PGA of the

filter added at the input.

TMP512/13 can be set to

÷2 to provide an 80mV

full-scale range.

Overload conditions are another consideration for the

TMP512/13

inputs.

The

TMP512/13

inputs

are

specified to tolerate 26V across the inputs. A large

FILTERING AND INPUT CONSIDERATIONS

differential scenario might be a short to ground on the

Measuring current is often noisy, and such noise can

load side of the shunt. This type of event can result in

be difficult to define. The TMP512/13 offer several

full power-supply voltage across the shunt (as long

options for filtering by choosing resolution and

the power supply or energy storage capacitors

averaging in Configuration Register 1. These filtering

support it). It must be remembered that removing a

options can be set independently for either voltage or

short to ground can result in inductive kickbacks that

current measurement.

could exceed the 26V differential and common-mode

rating of the TMP512/13. Inductive kickback voltages

The internal ADC is based on a delta-sigma (

ΔΣ)

are best dealt with by zener-type transient-absorbing

front-end with a 500kHz (

±10%) typical sampling rate.

devices (commonly called transzorbs) combined with

sufficient energy storage capacitance.

Figure 30. TMP512/13 with Input Filtering

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