Diodes ZXCT1020 User Manual

ZXCT1020

S+

GND

OUT

S-

V

B

Top view

1

2

3

5

4

Low offset current output current monitor

Description

The ZXCT1020 is a precision high-side current
sense monitor. Using this type of device
eliminates the need to disrupt the ground
plane when sensing a load current.

The ZXCT1020 uses two external resistors to
set the overall voltage gain for applications
where improved accuracy at small sense
voltages is required. For fixed gain variants
Zetex offers the ZXCT1021 (G=10) and
ZXCT1022 (G=100).

The ZXCT1020 footprint follows that of the
ZXCT1021/2 with only 2 additional resistors
required:

One resistor between pins 1 and 4 for setting
transconductance, and the other between
pins 3 and 2 for setting overall gain.

Current output enables the user to set the gain
via these external resistors. Using two external
resistors to set the gain ensures optimal
versatility as the transconductance can be varied
to meet the output impedance requirements of
the load that the ZXCT1020 has to drive.

The very low offset voltage enables a typical
accuracy of 3% for sense voltages of only 10mV,
giving better tolerances for small sense
resistors necessary at higher currents.

The wide input voltage range of 20V down to as
low as 2.5V make it suitable for a range of
applications. With a minimum operating current
of just 25µA, combined with its SOT23-5
package make it suitable for portable battery
equipment too.

ZXCT1020

Features

• Accurate high-side current sensing

• Versatile current output scaling

• 2.5V - 20V operating range

• 25µA quiescent current

• 1% typical accuracy

• SOT23-5 package

Applications

• Battery chargers

• Over-current monitor

• Motherboard power supply current measurement

• Level translating

• Programmable current source

Pinout information Typical application circuit

R

S

R

SH

S+

V

B

1

4

-

+

V

OUT

R

G

3

ZXCT1020

2

GND

I

L

S­(LOAD)

5

Ordering information

Order reference Package Device

marking

ZXCT1020E5TA SOT23-5 1020 Preview 7 3000 8

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© Zetex Semiconductors plc 2007

Status Reel size

(inches)

Quantity

per reel

Tape width

(mm)

ZXCT1020

NOTES:

Absolute maximum ratings

Voltage on VB with respect to GND pin -0.5V to 20V

(a)

Voltage on S+

SENSE

(c)

V

(b)

, S-

, OUT with respect to GND pin

Junction temperature -40°C to125°C
Storage temperature -55°C to 150°C
Package power dissipation (T

NOTES:

(a) Subject to V
(b) Subject to absolute maximum V
(c) V

(d) V

is defined as the voltage difference across the sense resistor. and is the voltage across resistor RSH plus the

SENSE

voltage between S+ and S-.

might need to be reduced when used with smaller values of RSH and at larger rails due to increased power dissipation.

SENSE

+ never going 6V below VB.

SENSE

= 25°C) SOT23-5 300mW

amb

not being exceeded.

SENSE

Pin out information

Pin Name Pin function

1 S+ Positive sense input. Should be tied to positive side of sense resistor via

resistance (R

2 GND Ground and substrate connection of device.
3 OUT Current output. A gain setting resistor (R

connected to this pin to set overall voltage gain of:

Gain = R

The resistance, RG, placed on out will set the ZXCT1020 output impedance equal

. When driving low impedance loads both RG and RSH should be reduced.

to R

G

4V

B

Input voltage pin. Provides bias to current monitor and should be tied to the
rail whose current is being monitored.

5 S- High impedance negative sense voltage input

) of the order of 150⍀ to 1.5k⍀.

SH

G/RSH

) referenced to GND should be

G

-0.5V to V

+0.5V

B

-0.5V to +2.5V

(d)

Recommended operating conditions

Parameter Min. Max. Units

V

SENSE+

V

B

V

SENSE

V

OUT

R

SH

T

A

(*) For best performance VB and V

Common-mode sense input range 2.5 20 V

Bias pin input voltage range

(*)

2.5 20 V

Differential sense Input voltage range 0 1.5 V

Output voltage range 0 V

SENSE-

- 1 V

Shunt resistor value 120 2000 ⍀

Ambient temperature range -40 85 °C

should be referred to the rail whose current is being measured.

SENSE+

Recommended resistor gain setting combinations

Gain R

SHUNT

10 1.5k⍀ 15k⍀
20 750⍀ 15k⍀
50 300⍀ 15k⍀

100 150⍀ 15k⍀

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R

GAIN

ZXCT1020

Electrical characteristics

T

= 25°C, V

amb

SENSE+

Symbol Parameter Conditions Limits Unit

V

OUT

Output voltage V

TC[1] Output voltage temperature

coefficient

I

Q

I

S-

I

+ S+ input current V

S

Ground pin current V

S- input current V

Acc Accuracy V

Gain V

R

OUT

OUT

Output resistance RG not connected 370 M⍀

BW Bandwidth V

PSRR Power supply rejection ratio V

= VB = 15V, V

/V

SENSE

= 100mV, RG = 15k⍀, RSH = 1.5k⍀ unless otherwise stated.

SENSE

Min. Typ. Max.

= 0mV 3 15 mV

SENSE

V

V

V

= 30mV 291 300 309 mV

SENSE

= 100mV 0.98 1 1.02 V

SENSE

= 150mV 1.47 1.5 1.53 V

SENSE

50 300 ppm

= 0V 25 35 ␮A

SENSE

= 0V 20 100 nA

SENSE

= 0V 100 nA

SENSE

= 100mV -2 2 %

SENSE

V

V

= 100mV 10 V/V

SENSE

(DC) = 10mV 300 kHz

SENSE

(DC) = 100mV 2 MHz

SENSE

SENSE+

= VB = 2.5 to 20V 70 80 dB

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Typical characteristics

ZXCT1020

Test conditions unless otherwise stated: TA = 25°C, VB = V
R

= 1.5k⍀, RG = 15k⍀.

SH

Supply current v Temperature

SENSE+

(via RSH) =15V, V

SENSE

= 100mV

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© Zetex Semiconductors plc 2007

ZXCT1020

°

°

°

°

°

°

°

°

°

°

°

°

°

°

°

Test conditions unless otherwise stated: TA = 25°C, VB = V
Gain = 10, R

= 15k⍀.

G

SENSE+

(via RSH) =15V, V

SENSE

= 100mV

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ZXCT1020

Test conditions unless otherwise stated: TA = 25°C, VB = V
Gain = 20, R

= 15k⍀.

G

°

°

°

°

°

SENSE+

°

(via RSH) =15V, V

°

°

SENSE

= 100mV

°

°

°

°

°

°

°

°

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© Zetex Semiconductors plc 2007

ZXCT1020

°

°

°

°

°

°

°

V

SENSE

= 10mV

Gain = 100

Test conditions unless otherwise stated: TA = 25°C, VB = V
R

= 15k⍀.

G

SENSE+

(via RSH) =15V, V

SENSE

= 100mV

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© Zetex Semiconductors plc 2007

Typical AC characteristics

Gain = 10

Gain = 50

Test conditions unless otherwise stated: TA = 25°C, VB = V
R

= 15k⍀.

G

SENSE+

ZXCT1020

(via RSH) =15V, V

SENSE

= 100mV,

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ZXCT1020

Various gains with constant R

G

Test conditions unless otherwise stated: TA = 25°C, RG=15k, VB = V
V

= 100mV unless otherwise stated.

SENSE

SENSE+

(via RSH) =15V,

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ZXCT1020

Test conditions unless otherwise stated: TA = 25°C, G=100, RG = 15k, VB = V
V

SENSE

= 100mV.

SENSE+

(via RSH),

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© Zetex Semiconductors plc 2007

ZXCT1020

V

OUT

R

G

R

SH

----------

V

SENSE

×=

Application information

The ZXCT1020 has a VB pin that is used to provide power to the current monitor. The maximum
voltage applied to the ZXCT1020 must be applied to this pin. The S+ and S- pins are used to
measure the current flowing to the load through the sense resistor. In normal use, the S+ is tied
to V

via a shunt resistor, RH making the ZXCT1020 essentially line powered.

B

The ZXCT1020 has a programmable gain set by the ratio of two external resistors R

I

L

S­(LOAD)

R

SH

V

R

S

B

and RSH.

G

S+

1

4

5

-

+

V

OUT

R

G

sets the transconductance whereas RG set the gain and results in an output voltage defined

R

SH

as:

Where V

The ZXCT1020 has been tested to the same conditions as the ZXCT1021 giving an overall voltage
gain of 10. The gain of the ZXCT1020 can be adjusted simply by varying R
of 50 R

Decreasing R
reduce the overall output impedance.

is increased from 15k⍀ to 75k⍀. An alternative is to decrease RSH from 1.5k⍀ to 300⍀.

G

SH

= R

SENSE

increases the transconductance and, if for any given gain, reducing the RSH will

SENSE

x I

3

ZXCT1020

2

GND

L

. So to achieve a gain

G

To achieve a gain of 100, for example, the following resistor values could be used:

R

= 150 RG = 15k

SH

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© Zetex Semiconductors plc 2007

ZXCT1020

Intentionally left blank

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© Zetex Semiconductors plc 2007

Package outline - SOT23-5

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°

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

ZXCT1020

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© Zetex Semiconductors plc 2007

ZXCT1020

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

or

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”
“Obsolete” Production has been discontinued

Datasheet status key:

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

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

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

Zetex sales offices

Europe

Zetex GmbH
Kustermannpark
Balanstraße 59
D-81541 München
Germany
Telefon: [phone]
Fax: [phone]
[e-mail]

© 2007 Published by Zetex Semiconductors plc

Device is still in production to support existing designs and production

may change in any manner without notice.

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

specifications may occur, at any time and without notice.

Americas

Zetex Inc
700 Veterans Memorial Highway
Hauppauge, NY 11788
USA

Telephone: [phone]
Fax: [phone]
[e-mail]

Asia Pacific

Zetex (Asia Ltd)
3701-04 Metroplaza Tower 1
Hing Fong Road, Kwai Fong
Hong Kong

Telephone: [phone]
Fax: [phone]
[e-mail]

Corporate Headquarters

Zetex Semiconductors plc
Zetex Technology Park, Chadderton
Oldham, OL9 9LL
United Kingdom

Telephone: [phone]
Fax: [phone]
[e-mail]

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