ZXCT1012DAATA - Zetex Semiconductors

Issue 1 - December 2006 1 www.zetex.com

ZXCT1012

Reduced height micro-power current monitor

Description

Ordering information

The ZXCT1012 is a high side current sense

monitor. Using this type of device eliminates

the need to disrupt the ground plane when

sensing a load current.

The ZXCT1012 takes the voltage developed

across a small value resistor and translates it

into a proportional output current. A user

defined output resistor scales the output

current into a ground referenced voltage.

The ZXCT1012 has the accuracy specification of

the ZXCT1010 but in TSOT23-5, and TDFN3x3-5.

A minimum operating current of just 3.5µA,

combined with its TSOT23-5 package make it

suitable for portable battery equipment where

size and current consumption are critical.

The wide input voltage range down to as low as

2.5V make it suitable for a wide range of

applications requiring direct operation from a

battery.

Features

• 2.5V to 20V supply range

• 3.5µA quiescent current

• Current output - user set gain

• Thin package - TSOT23-5 and TDFN3x3-5

• Temperature range -40 to 85°C

Applications

• Battery fuel gauge

• Battery chargers

• Overcurrent monitor

• Power management

Pin connections Applications circuit

SENSE-

TSOT23-5

Pinout - top view

SENSE+

OUT

GND

SENSE+

SENSE-

TDFN3x3-5

Pinout - bottom view

OUT

SENSE+ SENSE-

LOAD

ZXCT1012

IN SENSE

Device Package Status Device

marking

Reel size

(inches)

Tape width

(mm)

Quantity

per reel

ZXCT1012DAATA

TDFN-5 (3mm x 3mm)

Active 1012 7 8 3000

ZXCT1012ET5TA TSOT23-5 Active 1012 7 8 3000

ZXCT1012

Issue 1 - December 2006 2 www.zetex.com

Pin information

Absolute maximum ratings

Operation above the absolute maximum rating may cause device failure.

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

NOTES:

(‡) VSENSE is defined as the differential voltage between the SENSE+ and SENSE- pins.

VSENSE = VSENSE+ - VSENSE-

(†) Exposed lead not connected to thermal plane

Pin Name Description

TDFN5

TSOT23-5

3 1 N/C No connection

2 2 GND Ground connection

1 3 OUT Output current pin. Current generated due to a difference voltage

between VSENSE+ and VSENSE- flows out of this pin. A suitable

value resistor connected to ground creates an output voltage. The

maximum voltage out of this pin will be VSENSE- - 1.5V.

5 4 SENSE+ This pin should be connected to the rail whose current is being

measured and also provides power to internal circuitry. It is the

positive input of the current monitor and has an input range from

20V down to 2.5V. The current through this pin varies with

differential sense voltage.

4 5 SENSE- This is the negative input of the current monitor and has an input

range from 20V down to 2.5V.

VSENSE+ max. 20V

Voltage on any pin (relative to GND pin) -0.6 and VSENSE+ +0.5V

VSENSE(‡) -0.15V to +3V

Ambient operating temperature range -40 to 85°C

Storage temperature -55 to 150°C

Maximimum junction temperature 150°C

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

Package R⍜JA PDISS at 25°C

TSOT23-5 (*)

NOTES:

(*) Mounted on 30mm x 16mm x1.1mm FR4 board with 1oz copper.

250°C/W 500mW

TDFN3x3 5 pin(*) (†) 232°C/W 540mW

ZXCT1012

Issue 1 - December 2006 3 www.zetex.com

Recommended operating conditions

Electrical characteristics

Test conditions Tamb = 25°C, VIN = VSENSE+ = 5V, unless otherwise stated

Symbol Recommended parameter Limits

Min. Max. Units

VIN Sense+ range 2.5 20 V

TAAmbient temperature range differential -40 85 °C

VSENSE Sense voltage 10 2500 mV

VOUT Output voltage swing 0 VSENSE- -1.5 V

Symbol Parameter Conditions Limits Unit

Min. Typ. Max.

IOUT Output current VSENSE = 0V 0 0.3 15 ␮A

VSENSE = 10mV 85 100 115 ␮A

VSENSE = 40mV 380 400 420 ␮A

VSENSE = 100mV 0.975 1.00 1.025 mA

VSENSE = 200mV 1.95 2.00 2.05 mA

IQGround pin current VSENSE = 0V 3.5 8 ␮A

ISENSE- SENSE- pin input

current

100 nA

Acc Accuracy RSENSE = 0.1V

VSENSE = 200mV

-2.5 2.5 %

Gm Transconductance,

IOUT/VSENSE(*)

10 mA/V

Tc Temperature

coefficient

VSENSE = 200mV

Tamb = 0 to 50°C (*)

NOTES:

(*) Temperature dependent measurements are extracted from characterisation and simulation results.

(‡) With the ZXCT1012 using SENSE+ as its power supply pin, common mode rejection cannot be distinguished from

power supply rejection.

500 ppm/

°C

BW Bandwidth CL = 5pF,

ROUT = 1k⍀

VSENSE = 10mV

VSENSE = 100mV

300

kHz

MHz

CMRR

(‡)

Common mode

rejection ratio

VSENSE = 100mV, ROUT = 1k⍀

VIN = 2.5V to 20V

80 dB

ZXCT1012

Issue 1 - December 2006 4 www.zetex.com

Typical characteristics

-2%

-4%

-6%

ZXCT1012

Issue 1 - December 2006 5 www.zetex.com

Applications information

The ZXCT1012 current monitor works by converting the voltage developed across a small sense

resistor into a current on the out pin. In reality it is a voltage to current converter. This output

current can be converted into a voltage simply by passing it through a resistor (ROUT) to ground.

The current monitor has a transconductance of 10mA/V. But the overall amplifying conversion is

affected by both the RSENSE and ROUT

The gain equation of the ZXCT1012 is:

For best performance RSENSE should be connected as close to the SENSE+ (and SENSE-) pins;

which minimizes any series resistance with RSENSE and potential for interference pickup.

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 ZXCT1012 has been designed to provide best

performance with VSENSE of the order of 40mV to 200mV.

Current monitors are single supply devices which means they tend to saturate at very low sense

voltages. However it does mean the output can never go negative. Also the output can never

change direction (monotonic). This is important if the current monitor is used in a control loop.

As the sense voltage is reduced the output will tend to saturate as the input offset voltage starts

to have greater effect. It is recommended to have a minimum sense voltage of 10mV to minimize

linearity errors. Zetex has specified the output voltage at VSENSE of 10mV, 40mV, 100mV and

200mV; which is the recommended sense voltage range.

The maximum differential input voltage, VSENSE, is 2.5V; however this will cause large output

currents to flow increasing power dissipation in the chip. The sense voltage can be increased

further, without damaging the ZXCT1012, by the inclusion of a resistor, RLIM, between SENSE- pin

and the load. Typical values around 10k⍀. See figure below.

If large reverse currents are expected then the resistor, RLIM, will provide protection from

exceeding absolute maximum ratings.

A suitable value for RLIM can be determined from:

Where VSENSE(REV) is the maximum expected reverse sense voltage generated.

VOUT ILRSENSE

×ROUT

100

---------------

ZXCT1012

SENSE

RLIM

VSENSE REF()

5mA

-----------------------------------»

ZXCT1012

Issue 1 - December 2006 6 www.zetex.com

The following lines describe how to scale a load current to an output voltage.

VSENSE = RSENSE * ILOAD equation (1)

IOUT = 10mA/V x VSENSE equation (2)

VOUT = IOUT x ROUT equation (3)

Design example

In the circuit below a 1A current is to be represented by a 100mV output voltage (VOUT):

A) To be within recommended values choose the value of RSENSE to give:

50mV > VSENSE > 200mV at full load.

For example set VSENSE = 100mV at 1.0A.

From equation (1)

SENSE = 0.1V/1.0A = 0.1⍀

B) Now choose ROUT to give:

VOUT = 100mV, when VSENSE = 100mV.

From equation (2)

IOUT = 10mA/V x 0.1 = 1mA

Rearranging equation (3) for ROUT gives:

ROUT = VOUT/IOUT = 0.1/0.001 = 100⍀

= 0.1 / (0.1 x 0.01) = 100⍀

Typical circuit application

Where RLOAD represents any load including DC motors, a charging battery or further circuitry that

requires monitoring, Rsense can be selected on specific requirements of accuracy, size and power

rating.

OUT

OUTGND

SENSE+ SENSE-

LOAD

ZXCT1012

IN SENSE

ZXCT1012

Issue 1 - December 2006 7 www.zetex.com

Power dissipation

The maximum allowable power dissipation of the device for normal operation (PMAX), is a

function of the package junction to ambient thermal resistance (⍜JA), maximum junction

temperature (TJMAX), and ambient temperature (Tamb), according to the expression:

PMAX = (TJMAX – Tamb) / ⍜JA

The device power dissipation, PD is given by the expression:

PD=IOUT.(VIN-VOUT) watts

Care must be taken when using this device at large input voltages and large sense voltages to

prevent too much power dissipation.

VIN = 20V VSENSE = 2.5V

ROUT = 100⍀

IOUT = 2.5 x 0.01

= 25mA

VOUT = IOUT x ROUT

= 25mA x 100⍀

= 2.5V

∴ PD= 25mA (20 - 2.5)V

= 438mW

Power Dissipation

100

200

300

400

500

600

0 255075100125150

empera

ure

(°C)

PD - Power Dissipation

(mW)

TDF N3x 3 -5

TSOT23-5

ZXCT1012

Issue 1 - December 2006 8 www.zetex.com

Package outline - TSOT23-5

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

DIM Millimeters Inches

Min. Max. Min. Max.

A - 1.00 - 0.0393

A1 0.01 0.10 0.0003 0.0039

A2 0.84 0.90 0.0330 0.0354

b 0.30 0.45 0.0118 0.0177

c 0.12 0.20 0.0047 0.0078

D 2.90 BSC 0.114 BSC

E 2.80 BSC 0.110 BSC

E1 1.60 BSC 0.062 BSC

e 0.95 BSC 0.0374 BSC

e1 1.90 BSC 0.0748 BSC

L 0.30 0.50 0.0118 0.0196

L2 0.25 BSC 0.010 BSC

a° 4° 12° 4° 12°

ZXCT1012

Issue 1 - December 2006 9 www.zetex.com

DAA package outline - TDFN3x3-5

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

Dim. Millimeters Inches Dim. Millimeters Inches

Min. Max. Min. Max. Min. Max. Max. Max.

A 0.70 0.80 0.0276 0.0315 e 0.95REF 0.0374REF

A1 0.00 0.05 0.00 0.002 E 3.00BSC 0.1181BSC

A3 0.20REF 0.0079REF E2 0.85 1.10 0.0335 0.0433

b 0.30 0.45 0.0118 0.0177 L 0.30 0.50 0.0118 0.0197

D 3.00BSC 0.1181BSC K 0.20 - 0.0079 -

D2 1.85 2.10 0.0728 0.0827 - - - - -

E2/2

D2/2

ZXCT1012

Issue 1 - December 2006 10 www.zetex.com

Zetex sales offices

Europe

Zetex GmbH

Kustermann-park

Balanstraße 59

D-81541 München

Germany

Telefon: (49) 89 45 49 49 0

Fax: (49) 89 45 49 49 49

europe.sales@zetex.com

Americas

Zetex Inc

700 Veterans Memorial Highway

Hauppauge, NY 11788

USA

Telephone: (1) 631 360 2222

Fax: (1) 631 360 8222

usa.sales@zetex.com

Asia Pacific

Zetex (Asia Ltd)

3701-04 Metroplaza Tower 1

Hing Fong Road, Kwai Fong

Hong Kong

Telephone: (852) 26100 611

Fax: (852) 24250 494

asia.sales@zetex.com

Corporate Headquarters

Zetex Semiconductors plc

Zetex Technology Park, Chadderton

Oldham, OL9 9LL

United Kingdom

Telephone: (44) 161 622 4444

Fax: (44) 161 622 4446

hq@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

All products are sold subjects to Zetex’ terms and conditions of sale, and this disclaimer (save in the event of a conflict between the two

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.

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.