ZXCT1010
Document number: DS33442 Rev. 11 - 2
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ENHANCED HIGH-SIDE CURRENT MONITOR
Description
The ZXCT1010 is a high side current sense monitor. Using this
device eliminates the need to disrupt the ground plane when sensing
a load current.
It is an enhanced version of the ZXCT1009 offering reduced typical
output offset and improved accuracy at low sense voltage.
The wide input voltage range of 20V down to as low as 2.5V make it
suitable for a range of applications. A minimum operating current of
just 4µA, combined with its SOT25 package make suitable for
portable battery equipment.
Features
• Low cost, accurate high-side current sensing
• Output voltage scaling
• Up to 2.5V sense voltage
• 2.5V to 20V supply voltage range
• 300nA typical offset current
• 3.5µA quiescent current
• 1% typical accuracy
• SOT25 package
• Totally Lead-Free & Fully RoHS Compliant(Note 1 & 2)
• Halogen and Antimony Free. “Green” Device(Note 3)
Pin Assignments
SOT25
Package Suffix - E5
1
2
3
5
4
V -
SENSE
V +
SENSE
I
OUT
GND
NC
Top View
Applications
• Battery chargers
• Smart battery packs
• DC motor control
• Over current monitor
• Power management
• Programmable current source
Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
Typical Applications Circuit
ZXCT1010
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Pin Descriptions
Pin Number Pin Name Function
1 NC No connection
2 GND Ground
3 IOUT Output current, proportional to VIN - VLOAD
4 VSENSE- Supply voltage
5 VSENSE+ Connection to load/battery
Functional Block Diagram
Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.)
Parameter Rating Unit
Voltage on any pin (relative to IOUT) -0.6 to +20 V
Continuous output current, IOUT 25 mA
Continuous sense voltage, VSENSE (Note 4) -0.5 to +0.5 V
Operating temperature, TA -40 to +85 °C
Storage temperature -55 to +125 °C
Package power dissipation(@TA = +25°C) SOT25 300 mW
Note: 4. Operation above the absolute maximum rating may cause device failure. Operation at absolute maximum ratings, for extended periods, may reduce
device reliability
Electrical Characteristics (@TA = +25°C, unless otherwise specified.)
Symbol Parameter Conditions Limits Units
Min Typ Max
VIN VCC range − 2.5 − 20 V
IOUT Output Current (Note 5)
VSENSE = 0V 0 0.3 10 µA
VSENSE = 10mV 85 100 115
VSENSE = 100mV 0.975 1.0 1.025
mA
VSENSE = 200mV 1.95 2.0 2.05
VSENSE = 1V 9.7 10.0 10.3
Iq Ground pin current VSENSE = 0V — 3.5 8 µA
VSENSE Sense Voltage (Note 6) 0 — 2500 mV
ISENSE- VSENSE - Input Current − — — 100 nA
ACC Accuracy RSENSE = 0.1Ω; VSENSE = 200mV -2.5 — 2.5 %
GM Transconductance, IOUT/VSENSE − — 10000 — µA/V
BW Bandwidth
VSENSE(DC) = 10mV, RF PIN = -40dBm (Note 7) — 300 — kHz
VSENSE(DC) = 100mV, RF PIN = -20dBm (Note
7) — 2 — MHz
Notes: 5. Include input offset voltage contribution
6. VSENSE is defined as the differential voltage between VSENSE+ and VSENSE-, VSENSE = VSENSE+ -VSENSE- =VIN-VLOAD = ILOAD * RSENSE
7. -20dBm = 63mVP-P into 50Ω
ZXCT1010
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Power Dissipation
The maximum allowable power dissipation of the device for normal operation (PMAX), is a function of the package junction temperature (TJ(MAX)),
and ambient temperature (TAMB), according to the expression.
PMAX = (TJ(MAX) – TAMB)/θJA
The device power dissipation, PD is given by the expression:
PD = IOUT*(VIN – VOUT) Watts
Application Information
The following lines describes how to scale a load current to an output voltage.
E.g.
A 1.0A current is to be represented by a 100mV output voltage:
1) Choose the value of RSENSE to give 50mV > VSENSE > 500mV at full load.
For example, VSENSE = 100mV at 1.0A. RSENSE = 0.1/1.0 = > 0.1ohms.
2) Choose ROUT to give VOUT = 100mV, when VSENSE = 100mV.
Rearranging for Rout gives:
ROUT = VOUT/(VSENSE x 0.01)
ROUT = 0.1/(0.1 x 0.01) = 100Ω
Typical Circuit Application:
When RLOAD represented 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.
VSENSE = VIN – VLOAD
VOUT = 0.01 x VSENSE x ROUT
Typical Application Circuit
ZXCT1010
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Application Information (cont.)
Li-ion Charger Circuit:
The figure below shows the ZXCT1010 supporting the Benchmarq bq2954 Charge Management IC. Most of the support components for the
bq2954 are omitted for clarity. This design also uses the Zetex FZT789A high current Super-b PNP as the switching transistor in the DC-DC step
down converter and the FMMT451 as the drive NPN for the FZT789A. The circuit can be configured to charge up to four Li-ion cells at a charge
current of 1.25A. Charge can be terminated on maximum voltage, selectable minimum current, or maximum time out, switching frequency of the
PWM loop is approximately 120kHz.
Bi-Directional Current Sensing:
The ZXCT1010 can be used to measure current bi-directionally, if two devices are connected as show below:
If the voltage V1 is positive with respect to the voltage V2 the lower device will be active, delivering a proportional output current to Rout. Due to the
polarity of the voltage across RSENSE, the upper device will be inactive and will not contribute to the current delivered to Rout. When V2 is more
positive than V1, current will be flowing in the opposite direction, causing the upper device to be active instead.
Non-linearity will be apparent at small values of VSENSE due to offset current contribution. Devices can use separate output resistors if the current
direction is to be monitored independently.
ZXCT1010
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Application Information (cont.)
Bi-Directional Transfer Function:
PCB Trace Shunt Resistor for Low Cost Solution:
The figure below shows output characteristics of the device when using a PCB resistive trace for a low cost solution in replacement for a
conventional shunt resistor. The graph shows the linear rise in voltage across the resistor due to the PTC of the material and demonstrates how this
rise in resistance value over temperature compensates for the NTC of the device.
The figure opposite shows a PCB layout suggestion. The resistor section is 25mm x 0.25mm giving approximately 150mΩ using 1oz copper. The
data for the normalized graph was obtained using a 1A load current and a 100Ω output resistor. An electronic version of the PCB layout is available
by request.
ZXCT1010
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Ordering Information
Part Number Reel Size Tape Width Quantity per Reel Part Marking Package
ZXCT1010E5TA 7” 8mm 3000 Units 101 SOT25
Note: 8. Pad layout as shown on Diodes Inc. suggested pad layout document AP02001, which can be found on our website at
http://www.diodes.com/datasheets/ap02001.pdf
Package Outline Dimensions (All dimensions in mm.)
Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version.
Suggested Pad Layout
Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for latest version.
SOT25
Dim Min Max Typ
A 0.35 0.50 0.38
B 1.50 1.70 1.60
C 2.70 3.00 2.80
D ⎯ ⎯ 0.95
H 2.90 3.10 3.00
J 0.013 0.10 0.05
K 1.00 1.30 1.10
L 0.35 0.55 0.40
M 0.10 0.20 0.15
N 0.70 0.80 0.75
α 0° 8°
⎯
All Dimensions in mm
Dimensions Value (in mm)
Z 3.20
G 1.60
X 0.55
Y 0.80
C1 2.40
C2 0.95
A
M
JL
D
B C
H
KN
X
Z
Y
C1
C2C2
G
ZXCT1010
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