Diodes ZXCT1012 User Manual

R

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR

Description

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 TSOT25.

A minimum operating current of just 3.5μA, combined with its TSOT25 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.

Pin Assignments

(Top View) 1

NC

GND

2

OUT

TSOT25

ZXCT1012

SENSE-

5

43

SENSE+

Features

• 2.5V to 20V supply range

• 3.5μA quiescent current

• Current output - user set gain

• Thin package - TSOT25

• Temperature range -40 to 85°C

Typical Application Circuit

V

Applications

• Battery fuel gauge

• Battery chargers

• Overcurrent monitor

• Power management

IN

SENSE

SENSE+ SENSE-

ZXCT1012

GND

OUT

R

LOAD

V

OUT

R

OUT

ZXCT1012

Document number: DS33444 Rev. 2 - 2

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ZXCT1012

Pin Descriptions

Pin Name Description

1 N/C 2 GND

3 OUT

4 SENSE+

5 SENSE-

Absolute Maximum Ratings (T

V Voltage on any pin(relative to GND pin) -0.6 and V V Ambient Operating Temperature Range -40 to 85 °C Storage Temperature -55 to 150 °C Maximum Junction Temperature 150 °C

Power Dissipation (TA = 25°C)

Max. 20 V

SENSE+

(Note 1) -0.15 to 3 V

SENSE

Package

(Note 2)

TSOT25 250°C/W 500mW

Recommended Operating Conditions

Symbol Parameter Min. Max. Units

VIN Sense+ range 2.5 20 V

TA Ambient temperature range differential -40 85 C

V

Sense voltage 10 2500 mV

SENSE

V

Output voltage swing 0 V

OUT

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

Notes: 1. V

2. Mounted on 30mm x 16mm x1.1mm FR4 board with 1oz copper.

is defined as the differential voltage between the SENSE+ and SENSE- pins. (V

SENSE

ZXCT1012

Document number: DS33444 Rev. 2 - 2

No connection Ground connection Output current pin. Current generated due to a difference voltage

between V value resistor connected to ground creates an output voltage. The maximum voltage out of this pin will be V 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. This is the negative input of the current monitor and has an input range from 20V down to 2.5V.

Description Rating Unit

R

P

θJA

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR

SENSE+

and V

= 25°C)

A

@ 25°C

DISS

flows out of this pin. A suitable

SENSE-

300

(De-rate to 0 at 150°C)

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- 1.5V.

+0.5 V

SENSE+

mW

-15 V

SENSE-

SENSE

= V

SENSE+

- V

SENSE-

)

September 2011

ZXCT1012

Electrical Characteristics (T

Symbol Parameter Conditions

I

Output Current

OUT

IQ Ground Pin Current V

I

SENSE- Pin Input Current 100 nA

SENSE-

ACC Accuracy Gm

TC Temperature Coefficient

BW Bandwidth

CMRR

(Note 4)

Notes: 3. Temperature dependent measurements are extracted from characterisation and simulation results.

4. With the ZXCT1012 using SENSE+ as its power supply pin, common mode rejection cannot be distinguished from power supply rejection.

Transconductance,I (Note 3)

Common Mode Rejection Ratio

ZXCT1012

Document number: DS33444 Rev. 2 - 2

OUT/VSENSE

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR

= 25°C, VIN = V

A

V

SENSE

V

SENSE

V

SENSE

V

SENSE

V

SENSE SENSE

R

SENSE

V

SENSE

V

SENSE

TA = 0 to 50°C (Note 3)

= 5pF

C

L

R

OUT

V

SENSE

VIN = 2.5V to 20V

SENSE+

= 0V = 10mV = 40mV = 100mV = 200mV = 0V 3.5 8 µA

= 0.1V = 200mV

= 200mV

= 1kΩ

= 100mV, R

= 5V; unless otherwise specified)

Limits

Min. Typ. Max.

V

SENSE

V

SENSE

= 10mV = 100mV = 1kΩ

OUT

0

85

380

0.975

1.95

-2.5 2.5 % 10 mA/V

500 ppm/°C

80 dB

0.3 100 400

1.00

2.00

300

2

15 115 420

1.025

2.05

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Unit

µA µA

µA mA mA

kHz

MHz

T

P

T

CURRENT

A

T

PUT CURRENT

A

G

A

d

OUT

P

U

T CUR

R

E

N

T (m

A

0

REJ

C

O

d

Typical Characteristics

ZXCT1012

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR

10m

) (

100µ

U

OUT

I, OU

) (m

-2%

V = 5V

IN

T = 25°C

A

Ω

R = 0

OUT

1m

10µ

1µ

100µ 1m 10m 100m 1

V (V)

SENSE

Ty pical Output vs. Sense Voltag e

2%

0%

V = 5V

IN

V = 0.2V

SENSE

R = 0

Ω

OUT

4

V = 5V

IN

T = 25°C

A

R = 0

Ω

3

OUT

2

Typical

1

0

OUTPUT CURRENT ERROR (%)

-1 1m 10m 100m 1

3

V = 5V

IN

°

T = 25C

A

V = 63.2mVpp

SENSE(AC)

V (V)

SENSE

Error vs. S ense Voltage

0

DC V = 0.01V

-3

B) IN (

SENSE

V = 0.1V

SENSE

-6

-4%

OUT

I, OU

-6%

12

10

)

OUT

I,

-40

V = 5V T = 25C R = 0

8

6

4

2

-20 0 20 40 60 80 TEMPERATURE (°C)

Output Cur r ent vs. Temperature

IN

°

A

OUT

Ω

V = 1V

SENSE

V = 0.8V

SENSE

V = 0.6V

SENSE

V = 0.4V

SENSE

V = 0.2V

SENSE

-9

-12

0.01 0.1 1 10 FREQUENCY (MHz)

Frequency Response

V = 5V

IN

°

T = 25C

A

-10

V = 63.2Vpp

SENSE(AC)

-20

-30

B) N (

-40

TI

-50

E

V = 0.01V

SENSE

-60

-70

V = 1V

SENSE

V = 0.1V

SENSE

V = 1V

SENSE

-80

0

102345

V , SUPPLY VOLTAGE (V)

IN

Tran sf er Characteristics

ZXCT1012

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-90 1 10 100 1k 10k

FREQUENCY (Hz)

Common Mode Rejection

100k 1M 10M

September 2011

ZXCT1012

Applications Information

The ZXCT1012 current monitor works by converting the voltage deve lope d across a sma ll se nse res istor into a c urrent on the out pin. In reality it is a voltage to current converter. This output current can be converted into a volta ge simply by passing it through a resistor (R

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

OUT

.

and R The gain equation of the ZXCT1012 is:

) to ground.

OUT

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR

SENSE

R

OUT

I

SENSE

L

V ×=

R

OUT

100

For best performance R resistance with R

SENSE

When choosing appropriate values for R

should be connected as close to the SENSE+ (and SENSE-) pins; which minimizes any series

SENSE

and potential for interference pickup.

a compromise must be reached between in-line sign al loss (including p otential

SENSE

power dissipation effects) and small signal accuracy. Higher values for R

best operation the ZXCT1012 has been designed to provide best performance with V

gives better accuracy at low load currents by reducing the inaccuracies due to internal offsets. For

SENSE

of the order of 40mV to 200mV.

SENSE

Current monitors are single supply devices which means they tend to saturate at ver y 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. Diodes has specified the output voltage at V

The maximum differential input voltage, V

of 10mV, 40mV, 100mV and 200mV; which is the recommended sense voltage range.

SENSE

, is 2.5V; however this will cause large output currents to flow increasing power

SENSE

dissipation in the chip. The sense voltage can be increased further, without damaging the ZXCT1012, by the inclus ion of a resistor, R

, between SENSE- pin and the load. Typical values around 10kΩ. See figure below.

LIM

R

SENSE

R

C

LIM

ZXCT1012

If large reverse currents are expected then the resistor, R A suitable value for R

Where V

SENSE(REV)

ZXCT1012

Document number: DS33444 Rev. 2 - 2

can be determined from:

LIM

R

LIM

is the maximum expected reverse sense voltage generated.

www.diodes.com

, will provide protection from exceeding absolute maximum ratings.

LIM

V

=

)REF(SENSE

mA5

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R

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR

Applications Information

(cont.)

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

= R

SENSE

I

= 10mA/V x V

OUT

V

= I

OUT

Design example

In the circuit below a 1A current is to be represented by a 100mV output voltage (V A) To be within recommended values choose the value of R 50mV > V For example set V From equation (1) R

SENSE

B) Now choose R V

OUT

From equation (2) I

OUT

Rearranging equation (3) for R R

OUT

V

IN

SENSE

= 0.1V/1.0A = 0.1Ω

= 100mV, when V

= 10mA/V x 0.1 = 1mA

= V

OUT/IOUT

* I

SENSE

OUT

x R

equation (1)

LOAD

equation (2)

SENSE

equation (3)

OUT

> 200mV at full load.

= 100mV at 1.0A.

SENSE

to give:

OUT

= 100mV.

SENSE

gives:

OUT

= 0.1/0.001 = 100Ω

SENSE

to give:

OUT

ZXCT1012

):

SENSE+ SENSE-

ZXCT1012

GND

OUT

R

LOAD

V

OUT

R

OUT

= 0.1 / (0.1 x 0.01) = 100Ω

Typical Circuit Application

Where R

represents any load including DC motors, a charging battery or further circuitry that requires monitoring, R

LOAD

can be selected on specific requirements of accuracy, size and power rating.

ZXCT1012

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SENSE

ZXCT1012

) watts

), maximum junction temperature (T

JA

Power Dissipation

The maximum allowable power dissipation of the device for normal operation (P ambient thermal resistance (θ expression:

= (T

P

MAX

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

OUT

Care must be taken when using this device at large input voltages and large sense voltages to prevent too much power dissipation.

600

500

400

– TA) / θJA

JMAX

.(VIN-V

OUT

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR

), is a function of the package junction to

MAX

), and ambient temperature (TA), according to the

JMAX

300

200

100

0

0 255075100125150

T , AMBIENT TEMPERATURE ( C)

A

VIN = 20V V

= 100Ω

R

OUT

I

= 2.5 x 0.01

OUT

= 25mA

= I

V

OUT

= 25mA x 100Ω = 2.5V

׵ P

= 25mA (20 - 2.5)V

D

= 438mW

x R

SENSE

OUT

= 2.5V

ZXCT1012

Document number: DS33444 Rev. 2 - 2

°

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ZXCT1012

θ

Ordering Information

Device Package Marking Reel Size Quantity

ZXCT1012ET5TA TSOT25 1012 7 3000 Tape & Reel

Package Outline Dimensions (All Dimensions in mm)

D

E1

A2

A

A1

Suggested Pad Layout

ZXCT1012

Document number: DS33444 Rev. 2 - 2

e1

e

5x b

Y1

REDUCED HEIGHT MICRO-POWER CURRENT MONITOR

E

C C

4x 1

θ

Y (5x)

X (5x)

www.diodes.com

c

L

8 of 9

L2

Dimensions Value (in mm)

C X Y

Y1

TSOT25

Dim Min Max Typ

A

A1 0.01 0.10 A2 0.84 0.90

D E

E1

b 0.30 0.45 c 0.12 0.20 e

e1

L 0.30 0.50

L2

θ 0° 8° 4°

θ1 4° 12°

All Dimensions in mm

1.00

−

− −

0.950

0.700

1.000

3.199

−

2.90

2.80

1.60

−

0.95

1.90

0.25

−

September 2011

ZXCT1012

DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY A ND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).

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Products described herein may be covered by one or more United Stat es, international or foreign patents pending. Product names and markings noted herein may also be covered by one or more United States, international or foreign trademarks.

Diodes Incorporated 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 Diodes Incorporated. As used herei n:

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 instructi ons for us e provided in the labeling 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 t o perform can be reasonably expected

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

Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by Diodes Incorporated. Further, Customers must fully indemnify Diodes Incorporated and its representatives agai nst any damages arising out of the use of Diodes Incorporated products in such safety-critic al, l ife support devic es or syst ems .

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REDUCED HEIGHT MICRO-POWER CURRENT MONITOR

IMPORTANT NOTICE

LIFE SUPPORT

ZXCT1012

Document number: DS33444 Rev. 2 - 2

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