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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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

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

= 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

= 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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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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