MAX9937AXKT Ver la hoja de datos (PDF) - Maxim Integrated

Número de pieza

componentes Descripción

Fabricante

MAX9937AXKT

Current-Sense Amplifier with Reverse-Battery Protection

Maxim Integrated 

MAX9937

Current-Sense Amplifier with

Reverse-Battery Protection

At frequencies below the output corner frequency, the

MAX9937 itself provides excellent 100dB (DC) com-

mon-mode rejection. At higher frequencies, as the CMRR

of the MAX9937 degrades, the output filter formed by

ROUT and COUT helps boost the common-mode rejection

of the circuit.

Input Common-Mode Voltages

> 28V and < 0V

Short-duration overvoltages on the battery line are isolat-

ed from the RSP and RSN pins of the MAX9937 by the

use of input resistors RRSP and RRSN. The input ESD

clamp structure is designed so that the device can with-

stand short-duration (< 1s) overvoltages up to 40V when

using resistors RRSP and RRSN of 500Ω or greater as

shown in the Typical Application Circuit.

Approximately 40mA flows out of each ESD diode during

this condition (20V/500Ω). This current is less than the

50mA absolute maximum specification for the RSN and

RSP pins.

Skewed Input Offset Voltage

for Production Calibration

Due to low temperature drift of input bias current and

input offset voltage in the MAX9937, the part can be used

to provide powerful application and system benefits not

normally attainable from other current-sense amplifiers

on the market. For example, input resistors RRSP and

RRSN can be intentionally mismatched so as to introduce

an external, controlled input offset voltage into the circuit.

Doing so allows microcontroller firmware to trim out input

offset voltages completely by using production-line cal-

ibration during the manufacturing process or in system

operation as long as a zero load- current condition is

forced. Only minimal temperature-drift-based errors in the

resistor and in the bias currents then remain.

VOS-FINAL = VOS + IB- x RRSN - IB+ x RRSP

while gain = ROUT/RRSP.

Since gain can be fixed by choosing ROUT and RRSP,

a positive offset voltage can be induced by varying the

value of RRSN compared to RRSP.

For example:

ROUT = 10kΩ, RRSP = 500Ω fixes gain = 20V/V. Now,

choosing RRSN = 2.5kΩ, and knowing ∆IB= ±12% of IB,

the additional VOS becomes:

∆VOS (max) = (5.6µA x 2500) ± (0.12 x 5.6µA x 2500) -

(5.6µA x 500) = 11.2mV ± 1.7mV

∆VOS (min) = (0.8µA x 2500) ± (0.12 x 0.8µA x 2500) -

(0.8µA x 500) = 1.6mV ± 0.24mV

Since the minimum extra VOS introduced into the part

is greater than the maximum VOS of the current-sense

amplifier (= 1mV), the output of the current-sense amplifi-

er is always greater than zero even at zero sense voltage,

thus allowing the current-sense amplifier to be calibrated

at zero input current.

Operation with VCC = 0V (Shutdown)

The input terminals go into a high-impedance mode

when VCC = 0, as shown by the input bias current in

shutdown 1µA specification. Due to the low 20µA sup-

ply current, this then becomes a convenient way to put

the amplifier in shutdown simply by using a digital I/O

port of a microcontroller to power up/down the current-

sense amplifier. This can be especially useful in certain

battery-operated applications that need to implement

flexible power-management schemes.

Pin Configuration

TOP VIEW

+

VCC 1

MAX9937

GND 2

5 RSP

OUT 3

4 RSN

SC70

Chip Information

PROCESS: BiCMOS

Package Information

For the latest package outline information and land patterns

(footprints), go to www.maximintegrated.com/packages. Note

that a “+”, “#”, or “-” in the package code indicates RoHS status

only. Package drawings may show a different suffix character, but

the drawing pertains to the package regardless of RoHS status.

PACKAGE

TYPE

5 SC70

PACKAGE

CODE

DOCUMENT NO.

LAND

PATTERN NO.

X5+1

21-0076

90-0188

www.maximintegrated.com

Maxim Integrated │  10

Share Link: