Diodes ZXCT1041 User Manual

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ZXCT1041 Bidirectional precision high-side current monitor

Description

The ZXCT1041 is a bidirectional precision highside current sense monitor. The output voltage is proportional to the differential input voltage. Direction of current flow is indicated by the Flag pin.

The ZXCT1041 provides a fixed gain of 10 for applications where minimal external components are required.

Features

• Bidirectional high side measurement

• Output voltage scaling x10

• 2.7V to 20V high side voltage

• 35µA quiescent current

• 1% typical accuracy

• SOT23-5 package

The very low offset voltage enables a typical accuracy of 2% 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 2.7V make it suitable for a range of applications.

A minimum operating current of just 40␮A, combined with a SOT23-5 package makes the ZXCT1041 particularly suitable for portable battery equipment.

Applications

• Battery management

• Over current monitor

• Battery gas gauging

• Motor control

Typical application circuit

Pin connections

Flag

S-

S+

S-

ZXCT1041

Flag

GND

OUT

S+

GND

OUT

Ordering information

Order code Package Partmark Reel size

(inches)

ZXCT1041E5TA SOT23-5 1041 7 8 3000

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Tape width

(mm)

Quantity

per reel

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Absolute maximum ratings

ZXCT1041

Voltage on VS- and V

S+

Voltage on all other pins -0.6V to (V

[(VS+) - (VS-)] +/-6V

sense

Operating temperature, T

-0.6 to 20V

-40 to 125°C

or VS-) +0.6V

S+

Storage temperature -55 to 150°C

Maximum junction temperature, T

Package power dissipation 300mW at T

Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability.

150°C

= 25°C (De-rate to zero at 150°C)

Recommended operating conditions

Parameter Min. Max. Units

S±

Flag Current direction flag output 0 V

SENSE

OUT

Common-mode sense input range 2.7 20 V

S±

Differential sense input voltage range 0 ±0.8 V

Output voltage range 0 VS± -1.5 V

Ambient temperature range -40 125 °C

Pin function table

Pin Name Description

1Flag

2 GND Ground pin

3 OUT Output voltage pin

4 S+ This is the positive input of the current monitor. It also acts as the supply

5 S- This is the negative input of the current monitor. The current through this

This is the current direction pin. It is open collector and allows the logic high level to be set independent of V

voltage. Low indicates VS+ is greater than V

S+

voltage pin providing current for internal circuitry. The current through this pin varies with differential sense voltage

pin varies with differential sense voltage

S-

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Electrical characteristics

ZXCT1041

Test conditions TA = 25°C, VS+ = 10V, V

SENSE

= 100mV

Symbol Parameter Conditions Min. Typ. Max. Units

S+

S-

OUT

Ground pin current 15 35 50 µA

VS+ input current V

VS- input current V

Output voltage

= 0V 10 17 24 µA

SENSE

= 0V 10 17 24 µA

SENSE

= +150mV 1.55 1.5 1.45 V

SENSE

[flag high]

= +100mV 1.02 1 0.98 V

SENSE

= +30mV 309 300 291 mV

SENSE

= 0V 0 15 mV

SENSE

= -30mV 285 300 315 mV

SENSE

= -100mV 0.95 1 1.05 V

SENSE

= -150mV 1.42 1.50 1.58 V

SENSE

= ±100mV 30 ppm/ºC

SENSE

OUT

TC V

[flag low] V

variation with

OUT

temperature

Gain V

OUT/VSENSE

Accuracy Total output error

= 100mV ±2 %

SENSE

(Gain + offset)

Accuracy Total output error

SENSE

= -100mV ±5 %

(Gain + offset)

BW Bandwidth V

CMRR V

common mode

S+

SENSE(DC)

SENSE(AC)

VIN = 2.7 to 20V 60 dB

= 100mV = 63mV

300 kHz

rejection ratio

Flag TP Flag trip point Referred to V

Flag low output

= 100␮A60200mV

SINK

SENSE

-2.5 +2.5 mV

voltage

Flag high leakage

VOH = 5V 1 ␮A

current

NOTES:

(a) V (b) Temperature dependent measurements are extracted from characterisation and simulation results.

= "VS+" - "VS-"

SENSE

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Typical characteristics

ZXCT1041

Conditions V

SENSE

+=10V, V

=100mV, TA=25°C unless otherwise stated.

SENSE

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Typical characteristics

ZXCT1041

Conditions V

Sense+ Pin Current (µA)

+=10V, V

SENSE

Voltage (V)

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

OUT

700 600 500 400 300 200 100

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

SENSE+

FLAG VCC = 5V R

= 50k

FLAG

& V

TA = -40°C to 125°C

v Sense Voltage

FLAG

v Sense Vo ltag e

=100mV, TA=25°C unless otherwise stated.

SENSE

(V)

SENSE

(V)

SENSE

300 250

(µA)

200 150

GND

100

FLAG VCC = 5V

(V) I

FLAG

700 600 500 400 300 200 100

Sense- Pin Current (µA)

= 50k

FLAG

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15

GND

-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

SENSE-

& V

SENSE

v S e nse Voltage

FLAG

SENSE

v Sense Vo ltag e

Flag Current 100µA

(V)

TA = -40°C to 125°C

(V)

-5

-10

Gain Error (%)

-15

Output Load Resis tan ce (Ω)

Error v Resistive Loading

150 100

-50

-100

Output Voltage Error (mV)

-150

-10 -5 0 5 10

Output Load Curren t (µA))

Error v Current Load ing

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Typical characteristics

ZXCT1041

Conditions V

Voltage (V)

Forward Large Signal Step Response

0.20

0.15

0.10

0.05

Voltage (V)

0.00

Forward Small Signal Step Re sp on se

+=10V, V

SENSE

2.0

1.5

1.0

0.5

0.0

-5 0 5 10 15 20 25 30

=100mV, TA=25°C unless otherwise stated.

SENSE

Time (µs)

SENSE

-5 0 5 10 15 20 25 30 35

Time (µs)

2.0

1.5

OUT

1.0

0.5

Voltage (V)

0.0

-5 0 5 10 15 20 25 30

SENSE

OUT

Time (µs)

Reverse La rge Sign al Step Resp o n se

0.20

0.15

OUT

0.10

0.05

Voltage (V)

0.00

-5 0 5 10 15 20 25 30 35

SENSE

OUT

Time (µs)

Reverse Sm all Signal Step R esp o ns e

5 4 3 2 1

Voltage (V)

-1

-2

-4-20246810

FLAG

SENSE X10

Time (µs)

Large Sig Zero Crossing Response

2.0

1.5

1.0

OUT

Voltage (V)

0.5

0.0

-4 -2 0 2 4 6 8 10

Time (µs)

Large Sig Zero Crossing Response

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Typical characteristics

ZXCT1041

Conditions V

Voltage (V)

Large Sig Zero Crossing Response

(V)

OUT

Small Sig Zero Crossing Resp on se

+=10V, V

SENSE

5 4 3 2 1 0

-1

-2 16 18 20 22 24 26 28 30

=100mV, TA=25°C unless otherwise stated.

SENSE

FLAG

SENSE X10

Time (µs)

5 4 3 2 1 0

-1

-2

-4 -2 0 2 4 6 8 10 12 14

SENSE X100

FLAG

Time (µs)

2.0

1.5

1.0

Voltage (V)

0.5

0.0 16 18 20 22 24 26 28 30

Time (us)

Large Sig Zero Crossing Response

0.20

0.15

(V)

0.10

OUT

0.05

0.00

-4 -2 0 2 4 6 8 10 12 14

Time (µs)

Small Sig Zero Crossing Resp on se

OUT

5 4 3 2 1

Vout (V)

-1

-2 16 18 20 22 24 26 28 30 32 34

SENSE X100

FLAG

Time (µs)

Small Sig Zero Crossing Response

0.20

0.15

0.10

OUT

Vout (V)

0.05

0.00 16 18 20 22 24 26 28 30 32 34

Time (µs)

Small Sig Zero Crossing Response

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Typical characteristics

ZXCT1041

Conditions V

Reject i on (d B )

Gain (dB )

+=10V, V

SENSE

70 60 50 40 30 20 10

-10 100 1k 10k 100k 1M

Vs+=2.7V Vs+=5.0V Vs+=10V Vs+=15V & 20V

=100mV, TA=25°C unless otherwise stated.

SENSE

=+100mVrms

SENSE

VAC=63mV

P-P

Frequency (Hz)

Forward CMRR

25 20 15 10

-10

-15

-20

-25

5 0

-5

=+100mV

SENSE

VAC=63mV

100k 1M

VS+=2.7V VS+=5.0V VS+=10V VS+=15V VS+=20V

P-P

Frequency (Hz)

Forward Frequency Response

70 60 50 40 30 20 10

Rejection (dB)

-10 100 1k 10k 100k 1M

Vs+=15V & 20V Vs+=10V Vs+=5.0V Vs+=2.7V

=-100mVrms

SENSE

VAC=63mV

Frequency (Hz)

Reverse CMRR

25 20 15 10

5 0

-5

-10

Gain (dB)

-15

-20

-25

=-100mV

SENSE

VAC=63mV

100k 1M

VS+=2.7V VS+=5.0V VS+=10V VS+=15V VS+=20V

P-P

Frequency (Hz)

Reverse Frequency Response

P-P

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ZXCT1041

Application information

The ZXCT1041 uses two current monitors in anti-parallel to provide bidirectional current measurement. The integrated resistors while having a broad actual value variance provide very good matching to one another; this provides very tight gain matching from forward current measurement to reverse current management and removes the need to trim the resistor values.

The internal transconductance setting resistors have a nominal value of 1.5k⍀ thereby setting the internal transconductance to 0.67mA/V of V are summed into an internal common gain-setting resistor of 15k⍀. This sets the overall gain to 10 which has a very small variance due to the very good matching of internal transistors.

To improve accuracy the offset of amplifier 1 is trimmed.

The direction of measured current flow is determined by comparing the voltages applied to the bases of transconductance transistors (Q1 and Q2). For maximum versatility the flag output uses an open collector; this allows the ZXCT1041 to monitor rails at a much higher potential than what the flag output is interfacing to.

S+ S-

. The outputs of both current monitors (current)

SENSE-

1.5k 1.5k

OUT

Flag

15k

GND

A common application for micro-power current monitors is measuring the discharge current of a rechargeable lithium ion/polymer battery. The ZXCT1041 enables measuring both the charge and discharge current into the battery and with its wide operating voltage of 2.5 to 20V enables it to measure the currents in to/ out of up to 4 cells connected in series.

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ZXCT1041

Load

Battery charger control

When choosing appropriate values for R

S-

ZXCT1041

GND

a compromise must be reached between in-line

SENSE

S+

Battery

Flag

OUT

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

Higher values for R

gives better accuracy at low load currents by reducing the inaccuracies

SENSE

due to internal offsets. For best operation the ZXCT1041 has been designed to operate with V

of the order of 50mV to 150mV.

SENSE

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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

ZXCT1041

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ZXCT1041

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.

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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.

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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.

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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 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

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.

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Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 usa.sales@zetex.com

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