Rainbow Electronics MAX9937 User Manual

19-4233; Rev 0; 8/08

Automotive Current-Sense Amplifier

with Reverse-Battery Protection

General Description

The MAX9937 is a tiny automotive grade current-sense
amplifier designed for unidirectional high-side current­sense applications. This device addresses major areas
of concern for automotive applications including load­dump protection up to +40V, reverse-battery protec­tion, and filtering for EMI and transient performance.

The MAX9937 also features a low input offset voltage of
±1.2mV (max) at +25°C with a low temperature drift of
just 1µV/°C (typ).

The MAX9937 is available in a 5-pin SC70 package and
is rated over the -40°C to +125°C temperature range.

Applications

Automotive Battery Current Sense

Fuse Box Current Sense

ECU Current Monitor

Pin Configuration appears at end of data sheet.

Features

♦ Reverse Battery and Load-Dump Protection

-20V to +40V

♦ +4V to +28V Input Common-Mode Range

♦ Flexible EMI Filtering

♦ Low V

♦ Low V

: ±1.2mV (max)

OS

Drift: 1µV/°C (typ)

OS

♦ 20µA Supply Current

♦ 350kHz, 3dB Small Signal Bandwidth

Ordering Information

PART TEMP RANGE

MAX9937AXK+T -40°C to +125°C 5 SC70 +ATB

+

Denotes a lead-free/RoHS-compliant package.

T = Tape and reel.

PIN-

PACKAGE

MARK

Typical Application Circuit

MAX9937

TOP

R

SENSE

RS+

R

RSP

499Ω

RSP

GND

V

= 4V

BAT

TO 28V

MAX9937

R

V

OUT

OUT

V

SENSE

=

R

RSP

GAIN =

________________________________________________________________

R

OUT

10kΩ

OUT

RS-

R

RSN

499Ω

RSN

BIAS

BLOCK

V

CC

MICROCONTROLLER

ADC

LOAD

5V

Maxim Integrated Products

1

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.

MAX9937

Automotive Current-Sense Amplifier
with Reverse-Battery Protection

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= 5V, V

BAT

= V

RS+

= 12V, V

SENSE

= (V

RS+

- V

RS-

) = 0, R

RSP

= R

RSN

= 500Ω, R

OUT

= 10kΩ, TA= -40°C to +125°C. Typical

values are at T

A

= +25°C, unless otherwise noted. See the

Typical Application Circuit

.) (Note 2)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

RSP, RSN to GND Voltage Continuous ..................-0.3V to +30V

RSP, RSN to GND Load-Dump Voltage Duration

(V

BAT

= 40V) with

Typical Application Circuit

.......................1s

RSP, RSN to GND Reverse-Battery Voltage Duration

(V

BAT

= -20V) with

Typical Application Circuit

........Continuous

Differential Input Voltage (RSP - RSN)................................±0.3V

V

CC

to GND...........................................................-0.3V to +6.0V

OUT to GND ...............................................-0.3V to (V

CC

+ 0.3V)

Output Short Circuit to Ground ..................................Continuous

Continuous Input Current into RSN, RSP* ........................±50mA

Continuous Input Current into OUT*.................................±25mA

Thermal Limits (Note 1)
5 SC70 Multiple-Layer PCB

Continuous Power Dissipation (T

A

= +70°C)

(derate 3.1mW/°C above +70°C)............................246.9mW

θ

JA

...............................................................................324°C/W

θ

JC

...............................................................................115°C/W

Operating Temperature Range .........................-40°C to +125°C

Junction Temperature......................................................+150°C

Lead Temperature (soldering, 10s) .................................+300°C

Lead Temperature (reflow) ..............................................+260°C

Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a 4-layer

board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial

.

*

Junction temperature rating due to power dissipation must also be observed.

DC CHARACTERISTICS

Input Common-Mode Voltage
Range

Supply Voltage Range V

Input Offset Voltage (Note 3) V

Common-Mode Rejection Ratio CMRR V

Power-Supply Rejection Ratio PSRR VCC = +2.7V to +5.5V 90 120 dB

Quiescent Supply Current I

Input Bias Current (Note 4) IB+, I

Input Bias Current Mismatch ΔIB / I

Input Current in Shutdown I

Voltage Gain Gain = R

Voltage Gain Error (Notes 3, 5)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

RSP

V

V

RSP

RSN

CC

OS

CC

+ I

,

Inferred from CMRR test 4 28 V

Inferred from PSRR test 2.7 5.5 V

TA = +25°C ±0.3 ±1.2

TA = -40°C to +125°C ±1.6

= +4V to +28V

BAT

VCC = 5V 20 55 µA

TA = +25°C 0.8 2 5.6

B-

TA = -40°C to +125°C 0.65 6.5

2 x (IB+ - IB-)/(IB++IB-)

B

TA = +25°C, V

RSN

TA = -40°C to +125°C, VCC = 0 10

OUT/RRSP

TA = +25°C ±0.2 ±1.5

= -40°C to +125°C ±2.0

T

A

TA = +25°C 100 120

= +125°C 90

T

A

TA = +25°C ±1 ±12 %

T

= -40°C to

A

+125°C

= 0 0.01 1

CC

20 V/V

±15 %

mV

dB

µA

µA

%

MAX9937

Automotive Current-Sense Amplifier

with Reverse-Battery Protection

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 5V, V

BAT

= V

RS+

= 12V, V

SENSE

= (V

RS+

- V

RS-

) = 0, R

RSP

= R

RSN

= 500Ω, R

OUT

= 10kΩ, TA= -40°C to +125°C. Typical

values are at T

A

= +25°C, unless otherwise noted. See the

Typical Application Circuit

.) (Note 2)

Note 2: All devices are 100% production tested at T

A

= +25°C. Temperature limits are guaranteed by design.

Note 3: Gain and offset voltage are calculated based on two point measurements: V

SENSE1

= 5mV and V

SENSE2

= 200mV.

Note 4: Input bias current I

B+

and IB-refers to the internal op amp’s inputs (inverting and noninverting) so that IB-= I

RSN

and

I

B+

= I

RSP

- I

OUT

.

Note 5: The gain is set by the external resistors R

RSP

and R

OUT

. See the

Typical Application Circuit.

Note 6: V

RSP

= V

BAT

- V

SENSE

- VOS- (R

RSN

x IB-).

Maximum Output Current I

Output-Voltage Compliance
(Note 6)

Output-Voltage High V

Output-Voltage Low V

AC CHARACTERISTICS

3dB Large-Signal Bandwidth BW V

3dB Small-Signal Bandwidth 350 kHz

Settling Time to 1% t

Input-Voltage Noise e

Input Current Noise I

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

R

II

BB

++-

I

=

B

Δ ||

2

III

=

BBB

OUT

OH

OL

S

n

n

= 500Ω, R

RSN

V

V

V
V

V

SENSE

= 4V, V

BAT

= 4V, V

BAT

= V

OH

= 4V, V

BAT

SENSE

= 500mV, ΔI

- V

BAT

= 137.5mV

f = 1kHz 28 nV/√Hz
f = 1kHz 1 pA/√Hz

+

-

-

= 0, V

RSP

OUT

= 0.1V, ΔI

SENSE

= +500mV,

SENSE

OUT

= -100mV 2 20 mV

SENSE

+ 225mV

DC

= 0 2 7.5 22 mA

OUT

≤ 1% -0.1

V

-

≤ 2% -0.1

OUT

RSP

0.15

0.4 1.2 V

P-P

250 kHz

V

V

5µs

CC

0.1

RSP

0.8

+

-

V

MAX9937

Automotive Current-Sense Amplifier
with Reverse-Battery Protection

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VCC= 5V, V

BAT

= V

RSP

= 12V, V

SENSE

= V

RS+

- V

RS-

= 0, R

RSP

= R

RSN

= 500Ω, R

OUT

= 10kΩ, TA= +25°C, unless otherwise noted.

See the

Typical Application Circuit

.)

0

200

100

400

300

500

600

-40 400 80 120 160

OFFSET VOLTAGE vs. TEMPERATURE

MAX9937 toc02

TEMPERATURE (°C)

OFFSET VOLTAGE (μV)

100

400

300

200

600

500

700

800

412168 202428

OFFSET VOLTAGE

vs. COMMON-MODE VOLTAGE

MAX9937 toc03

COMMON-MODE VOLTAGE (V)

OFFSET VOLTAGE (μV)

TA = +25°C

TA = +125°C

TA = -40°C

0

-700

-500

-400

-300

-200

-100

0

3.0 3.5 4.0 4.5 5.0

OFFSET VOLTAGE

vs. POWER-SUPPLY VOLTAGE

MAX9937 toc04

POWER-SUPPLY VOLTAGE (V)

OFFSET VOLTAGE (μV)

-600

TA = +125°C

TA = -40°C

TA = +25°C

AC COMMON-MODE REJECTION RATIO

C

IN

= 220nF

MAX9937 toc05

FREQUENCY (Hz)

CMRR (dBV)

100k10k1k10010

-100

-80

-60

-40

-20

0

-120
11M

C

LOAD

= 10pF

C

LOAD

= 1nF

C

LOAD

= 100pF

AC POWER-SUPPLY REJECTION RATIO

C

IN

= 220nF

MAX9937 toc06

FREQUENCY (Hz)

PSRR (dBV)

100k10k1k10010

-120

-100

-80

-60

-40

-20

0

-140
11M

C

LOAD

= 100pF

C

LOAD

= 10pF

C

LOAD

= 1nF

0

10

5

20

15

30

25

35

25 100 175 250 325 400 475 550

OFFSET VOLTAGE HISTOGRAM

MAX9937 toc01

OFFSET VOLTAGE (μV)

FREQUENCY (%)