ZXCT1051E5TA - Zetex Semiconductors

Issue 2 - November 2006 1 www.zetex.com

ZXCT1051

Precision wide input range current monitor

Description

The ZXCT1051 is a wide input range current

monitor, which operates over a range of input

voltages from ground up to VCC-2V. As a result

the ZXCT1051 can be used on the high or low

side of the load.

The very low offset voltage enables a typical

accuracy of 1% for sense voltages of only

30mV, giving better tolerances for small sense

resistors necessary at higher currents.

Features

• Accurate down to end current sensing

• Output voltage scaling x10

•0 to V

CC-2V sense input range

• 2.7 to 20V supply range

• 50 µA quiescent current

• 1% typical accuracy

• SOT23-5 package

Pin connections

The ZXCT1051 provides a fixed gain of 10

thereby removing the need for an additional

resistor.

Applications

• Power supply

• DC motor and solenoid control

• Battery management

• Over current monitor

• Power management

• Short circuit detection

Typical application circuit

Ordering information

VCC

GND

VOUT

VSENSE-

VSENSE+

ZXCT1051

VSENSE+

VCC

GND

VOUT

VSENSE-

VSENSE+RSENSE

Order code Package Partmark Reel size

(inches)

Tape width

(mm)

Quantity

per reel

ZXCT1051E5TA SOT23-5 1051 7 8 3,000

ZXCT1051

Issue 2 - November 2006 2 www.zetex.com

Absolute maximum ratings

VCC max. 20V

Voltage on VSENSE- and VSENSE+ -0.6 to VCC

Voltage on all other pins -0.6V and VCC +0.6V

VSENSE "(VSENSE+) - (VSENSE-) 500mV

Operating temperature, Tamb -40 to 125°C

Storage temperature -55 to 150°C

Maximum junction temperature 150°C

Package power dissipation 300mW at Tamb = 25°C (de-rate to zero at 150°C)

Operation above the absolute maximum rating may cause device failure. Operation at the

absolute maximum ratings, for extended periods, may reduce device reliability.

Recommended operating conditions

Pin function table

Parameter Min. Max. Units

VSENSE+ Common-mode sense input range 0 VCC-2 V

VCC Supply voltage range 2.7 20 V

VSENSE Differential sense input voltage range 0 0.3 V

VOUT Output voltage range 0 VCC - 2 V

Tamb Ambient temperature range -40 125 °C

Pin Name Description

CC This is the analog supply and provides power to internal circuitry

2 GND Ground pin

3 OUT Output voltage pin.

SENSE+ This is the positive input of the current monitor and has an input range from

0V up to VCC – 2V.

SENSE- This is the negative input of the current monitor and has an input range

from 0V up to VCC – 2V. The current through this pin varies with differential

sense voltage.

ZXCT1051

Issue 2 - November 2006 3 www.zetex.com

Electrical characteristics

Test conditions Tamb = 25°C, VSENSE+ = 10V, VCC = 12V, VSENSE = 100mV

NOTES:

(a) VSENSE = "VSENSE+" - "VSENSE-"

(b) Temperature dependent measurements are extracted from characterization and simulation results.

Symbol Parameter Conditions Min. Typ. Max. Units

IQVCC pin current VSENSE = 0V 45 70 µA

VOUT Output voltage VSENSE = 0V

=30mV

=100mV

=150mV

291

0.98

1.45

300

1.00

1.50

309

1.02

1.55

ISENSE+V

SENSE+ input current VSENSE = 0V 10 150 nA

ISENSE-V

SENSE- input current VSENSE = 0V 60 150 nA

VOUT TC VOUT variation with

temperature

See note (b) 300 ppm/°C

ROUT Output resistance 2.5 3.75 5 k⍀

Gain VOUT/VSENSE 10

Accuracy Total output error -2 2 %

BW Bandwidth VSENSE(DC)

= 10mV

VSENSE(AC)

= 10mVPP

CL = 5pF,

300 kHz

VSENSE(DC)

= 100mV

1MHz

PSRR Power supply

rejection ratio refered

to output

VCC = 2.7V to 20V

VSENSE- = 0V

58 dB

CMRR Common mode

rejection ratio refered

to output

VCC = 20V

VSENSE+ = 0 to 18V

66 dB

ZXCT1051

Issue 2 - November 2006 4 www.zetex.com

Typical characteristics

Supply Current v Input Voltage

ICC Supply Current (A)

Supply Current v Supply Voltage

ICC Supply Current (A)

Sense- Current v Supply Voltage

IS- Sense Current (A)

Sense- Current v Temperature

Percentage Change IS- (%)

Supply Current v Sense Voltage

ICC Supply Current (A)

Sense- Current v Sense Voltage

IS- Sense Current (A)

ZXCT1051

Issue 2 - November 2006 5 www.zetex.com

Typical characteristics

1E-3 0.01 0.1

10m

100m

-20 -15 -10 -5 0 5 10 15 20

900

950

1000

1050

1100

0 50m 100m 150m

9.9

10.0

10.1

0 2 4 6 8 101214161820

-8

-6

-4

-2

0 5 10 15 20

-12

-8

-4

-40 -20 0 20 40 60 80 100 120

-5

VOUT - Output Voltage (V)

OUT

v Load Current

VOUT - Output Voltage (mV)

Incremental Gain v Sense Voltage

Incremental Gain

Common Mode Characteristic

∆VOUT - Output Voltage (mV)

Supply Characteristic

∆VOUT - Output Voltage (mV)

Temperature Characteristic

∆VOUT Output Voltage (mV)

ZXCT1051

Issue 2 - November 2006 6 www.zetex.com

Typical characteristics

100 1k 10k 100k 1M 10M

-60

-50

-40

-30

-20

-10

0246810

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0246810

0.88

0.90

0.92

0.94

0.96

0.98

1.00

1.02

1000 10000 100000 1000000 1E7

100 1k 10k 100k 1M

0 5 10 15 20 25 30 35 40

Bandwidth

Gain (dB)

Large Signal Pulse Response

VOUT - Output Voltage (V)

Small Signal Pulse Response

VOUT - Output Voltage (V)

PSRR

Supply Rejection (dB)

CMRR

Common Mode Rejection (dB)

Turn on/off Characteristic

VOUT - Output Voltage (V)

ZXCT1051

Issue 2 - November 2006 7 www.zetex.com

Application information

The ZXCT1051 is Zetex’ first current monitor with a separate power supply pin. All biasing for the

internal amplifiers comes from its separate VCC input and is not ‘line powered’, unlike the

ZXCT1021.

This means that at very small sense voltages the ZXCT1051 draws very little current (<1µA) from

the lines being sensed.

The separate VCC pin enables the ZXCT1051 to be operated at sense line voltages down to 0V,

where the ZXCT1021 would switch off. This feature enables the ZXCT1051 to be used to sense the

currents flowing through lines that have been shorted to ground and is Zetex’ first current

monitor to do this.

Basic operation

Load current from VIN is drawn through RSENSE developing a voltage VSENSE across the

ZXCT1051.

The internal amplifier forces VSENSE across internal resistance RSH causing a current to flow

through transistor Q1. This current is then converted to a voltage by RG. A ratio of 10:1 between

RSH and RG creates the fixed gain of 10 with an output impedance equal to RG (see electrical

characteristics for output current-voltage characteristics).

The gain equation of the ZXCT1051 is:

The maximum differential input voltage, VSENSE, is 150mV (IL * RSENSE); however voltages up to

500mV will not damage it. This can be increased further by the inclusion of a resistor, RLIM,

between VSENSE- pin and the load.

For best performance RSENSE should be connected as close to the VSENSE+ and VSENSE- pins thus

minimizing any series resistance with RSENSE.

RSENSE

VSENSE+ VSENSE-

VOUT

VCC

VRAIL

RSH

GND

Load

VSENSE ILRSENSE

RSH

-----------1×=

ZXCT1051

Issue 2 - November 2006 8 www.zetex.com

The ZXCT1051 has been designed to allow it to operate from supplies (VCC) ranging from 2.7V to

20V while sensing common mode signals from 0V up to VCC -2V.

When choosing appropriate values for RSENSE a compromise must be reached between in-line

signal loss (including potential power dissipation effects) and small signal accuracy.

Higher values for RSENSE gives better accuracy at low load currents by reducing the inaccuracies

due to internal offsets. For best operation the ZXCT1051 has been designed to operate with

VSENSE of the order of 50mV to 150mV.

Due to the very nature of current monitors they tend to saturate at very low sense voltages. This

is due to them being operated from single supply and that the basic configuration is that of a

unipolar voltage to current to voltage converter. The internal amplifiers at the heart of the current

monitor may well have a bipolar offset voltage but the output cannot go negative.

For this reason the ZXCT1051 has been designed to operate in a linear manner over a VSENSE

range of 10mV to 150mV range, however it will still be monotonic down to VSENSE of 0V.

The device has a fixed DC voltage gain of 10; no external scaling resistors are required for the

output. Output voltage is simply defined as:

VOUT = gain x VSENSE (V)

ZXCT1051

Issue 2 - November 2006 9 www.zetex.com

Packaging details - SOT23-5

Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches

DIM Millimeters Inches

Min. Max. Min. Max.

A 0.90 1.45 0.0354 0.0570

A1 0.00 0.15 0.00 0.0059

A2 0.90 1.30 0.0354 0.0511

b 0.20 0.50 0.0078 0.0196

C 0.09 0.26 0.0035 0.0102

D 2.70 3.10 0.1062 0.1220

E 2.20 3.20 0.0866 0.1181

E1 1.30 1.80 0.0511 0.0708

e 0.95 REF 0.0374 REF

e1 1.90 REF 0.0748 REF

L 0.10 0.60 0.0039 0.0236

a° 0° 30° 0° 30°

ZXCT1051

Issue 2 - November 2006 10 www.zetex.com

Definitions

Product change

Zetex Semiconductors reserves the right to alter, without notice, specifications, design, price or conditions of supply of any product or

service. Customers are solely responsible for obtaining the latest relevant information before placing orders.

Applications disclaimer

The circuits in this design/application note are offered as design ideas. It is the responsibility of the user to ensure that the circuit is fit for

the user’s application and meets with the user’s requirements. No representation or warranty is given and no liability whatsoever is

assumed by Zetex with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights

arising from such use or otherwise. Zetex does not assume any legal responsibility or will not be held legally liable (whether in contract,

tort (including negligence), breach of statutory duty, restriction or otherwise) for any damages, loss of profit, business, contract,

opportunity or consequential loss in the use of these circuit applications, under any circumstances.

Life support

Zetex products are specifically not authorized for use as critical components in life support devices or systems without the express written

approval of the Chief Executive Officer of Zetex Semiconductors plc. As used herein:

A. Life support devices or systems are devices or systems which:

1. are intended to implant into the body

2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the

labelling can be reasonably expected to result in significant injury to the user.

B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to

cause the failure of the life support device or to affect its safety or effectiveness.

Reproduction

The product specifications contained in this publication are issued to provide outline information only which (unless agreed by the

company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a

representation relating to the products or services concerned.

Terms and Conditions

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when the terms of the contract shall prevail) according to region, supplied at the time of order acknowledgement.

For the latest information on technology, delivery terms and conditions and prices, please contact your nearest Zetex sales office or visit:

www.zetex.com

Quality of product

Zetex is an ISO 9001 and TS16949 certified semiconductor manufacturer.

To ensure quality of service and products we strongly advise the purchase of parts directly from Zetex Semiconductors or one of our

regionally authorized distributors. For a complete listing of authorized distributors please visit: www.zetex.com/salesnetwork

Zetex Semiconductors does not warrant or accept any liability whatsoever in respect of any parts purchased through unauthorized sales channels.

ESD (Electrostatic discharge)

Semiconductor devices are susceptible to damage by ESD. Suitable precautions should be taken when handling and transporting devices.

The possible damage to devices depends on the circumstances of the handling and transporting, and the nature of the device. The extent

of damage can vary from immediate functional or parametric malfunction to degradation of function or performance in use over time.

Devices suspected of being affected should be replaced.

Green compliance

Zetex Semiconductors is committed to environmental excellence in all aspects of its operations which includes meeting or exceeding

regulatory requirements with respect to the use of hazardous substances. Numerous successful programs have been implemented to

reduce the use of hazardous substances and/or emissions.

All Zetex components are compliant with the RoHS directive, and through this it is supporting its customers in their compliance with

WEEE and ELV directives.

Product status key:

“Preview” Future device intended for production at some point. Samples may be available

“Active” Product status recommended for new designs

“Last time buy (LTB)” Device will be discontinued and last time buy period and delivery is in effect

“Not recommended for new designs”

Device is still in production to support existing designs and production

“Obsolete” Production has been discontinued

Datasheet status key:

“Draft version” This term denotes a very early datasheet version and contains highly provisional information, which

may change in any manner without notice.

“Provisional version” This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance.

However, changes to the test conditions and specifications may occur, at any time and without notice.

“Issue” This term denotes an issued datasheet containing finalized specifications. However, changes to

specifications may occur, at any time and without notice.

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Fax: (49) 89 45 49 49 49

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