ZXCT1009
HIGH-SIDE CURRENT MONITOR
ZXCT1009
Document number: DS33441 Rev. 12 - 2 1 of 8
www.diodes.com April 2011
© Diodes Incorporated
Description
The ZXCT1009 is a high side current sense monitor. Using
this device eliminates the need to disrupt the ground plane
when sensing a load current.
It takes a high side voltage de veloped across a current shun t
resistor and translates it into a proportional output current. A
user defined output resistor scales the output current into a
ground-referenced voltage.
The wide input voltage range of 20V do wn to as low as 2.5V
make it suitable for a range of applications. A minimum
operating current of just 4µA, combined with a SOT23
package make it a unique solution for portable battery
equipment. The SM8 device offers an alternative package
option.
Features
• Low cost, accurate high-side current sensing
• Output voltage scaling
• Up to 2.5V sense voltage
• 2.5V to 20V supply range
• 4A quiescent current
• 1% typical accuracy
• SOT23 and SM8 packa ges
• AEC-Q100.3 qualified; ZXCT1009FTA only
Applications
• Battery chargers
• Smart battery packs
• DC motor control
• Over current monitor
• Power management
• Level translating
• Programmable current source
•
Pin Assignments
SOT23
Package Suffix - F
SM8
Package Suffix – T8
Application Circuit
IOUT
VSENSE+
3VSENSE-
(Top View)
2
1IOUT
VSENSE+
3VSENSE-
(Top View)
2
1
IOUT N/C
VSENSE- N/C
(Top View )
4
2
3
1
5
7
6
8
N/C
VSENSE+
N/C
N/C
IOUT N/C
VSENSE- N/C
(Top View )
4
2
3
1
5
7
6
8
N/C
VSENSE+
N/C
N/C
VIN RSENSE To loa d
VOUT
ROUT
1
23
ZXCT1009
VSENSE+ VSENSE-
IOUT
VIN RSENSE To loa d
VOUT
ROUT
1
23
ZXCT1009
VSENSE+ VSENSE-
IOUT
ZXCT1009
HIGH-SIDE CURRENT MONITOR
ZXCT1009
Document number: DS33441 Rev. 12 - 2 2 of 8
www.diodes.com April 2011
© Diodes Incorporated
Pin Descriptions
Pin Name Pin Function
VSENSE+ Connection to supply voltage
VSENSE- Connection to load
IOUT Output current, proportional to measured current
Absolute Maximum Ratings (TA = 25°C)
Description Rating Unit
Voltage on any pin (relative to IOUT) -0.6 to 20 V
Continous output current, IOUT 25 mA
Continuous sense voltage, VSENSE† -0.5 to +5 V
Operating temperature, TA -40 to 85 °C
Storage temperature -55 to 125 °C
Package power
dissipation @ TA = 25°C
(Derate to zero @ 125°C)
SOT23 450 mW
SM8 2 W
Operation above the absolute maximum rating may cause device failure. Operation at the absolute
maximum ratings for extended periods may reduce device reliability.
Electrical Characteristics (TA = 25°C, VIN = 5V, ROUT = 100Ω)
Symbol Parameter Conditions Limits Units
Min Typ Max
VIN V
CC range 2.5 20 V
IOUT1 Output Current
VSENSE = 0V
VSENSE = 10mV
VSENSE = 100mV
VSENSE = 200mV
VSENSE = 1V
1
90
0.975
1.95
9.6
4
104
1.002
2.0
9.98
15
120
1.025
2.05
10.2
µA
µA
mA
mA
mA
VSENSE† Sense Voltage 0 2500 mV
ISENSE- VSENSE -
Input Current 100 nA
ACC Accuracy RSENSE = 0.1
VSENSE = 200mV
-2.5
2.5
%
GM Transconductance,
IOUT/VSENSE 10000 µA/V
BW Bandwidth VSENSE(DC) = 10mv, RF PIN = -40dBm‡
VSENSE(DC) = 100mv, RF PIN = -20dBm‡ 300
2 kHz
MHz
Notes: 1. Includes input offset voltage contribution
†. VSENSE is defined as the differential voltage between VSENSE+ and VSENSE-.
VSENSE = VSENSE+ - VSENSE-
= VIN - VLOAD
= ILOAD x RSENSE
‡ -20dBm=63mVPP into 50
ZXCT1009
HIGH-SIDE CURRENT MONITOR
ZXCT1009
Document number: DS33441 Rev. 12 - 2 4 of 8
www.diodes.com April 2011
© Diodes Incorporated
Typical Characteristics (cont.)
Power Dissipation
The maximum allowable power dissipation of the device for
normal operation (PMAX), is a function of the package junction to
ambient thermal resistance (JA), maximum junction temp erature
(TJMAX), and ambient temperature (TAMB), according to the
expression:
PMAX = (TJMAX – TAMB) / JA
The device power dissipation, PD is given by the expression:
PD = IOUT(VIN -VOUT) W
Application Information
The following text describes how to scale a load current
to an output voltage.
VSENSE = VIN - VLOAD
VOUT = 0.01 x VSENSE x ROUT1
E.g.
A 1A 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 => 0.1.
2) Choose ROUT to give VOUT = 100mV, when
VSENSE = 100mV.
Rearranging 1 for Rout gives:
ROUT = VOUT /(VSENSE x 0.01)
ROUT = 0.1 / (0.1 x 0.01) = 100
ZXCT1009
HIGH-SIDE CURRENT MONITOR
ZXCT1009
Document number: DS33441 Rev. 12 - 2 5 of 8
www.diodes.com April 2011
© Diodes Incorporated
Application Information (cont.)
Li-Ion Charger Circuit
The above figure shows the ZXCT1009 supporting the
Benchmarq bq2954 Charge Management IC. Most of the
support components for the bq2954 are omitted for clarity.
This design also uses the Diodes FZT789A high current
Super-ß 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 u p 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.
The ZXCT1009 is intended as a direct functional
replacement for the ZDS1009, which is featured in a
complete design from Unitrode/Texas Instruments on the
Li-Ion charger circuit shown above. Reference:
DVS2954S1H Li-Ion Charger Development System.
Transient Protection
A
n additional resistor, RLIM can be added in series with ROUT
(as below), to limit the current from IOUT. Any circuit
connected to VOUT will be protected from input voltage
transients. This can be of particular use in automotive
applications where load dump and other common transients
need to be considered.
ZXCT1009 with additional current limiting Resistor RLIM.
A
ssuming the worst case condition of VOUT = 0V; providing a
low impedance to a transient, the minimum value of RLIM is
given by:-
RLIM(min) = (VPK – VMAX)/IPK
VPK = Peak transient voltage to be withstood
VMAX = Maximum working voltage = 20V
IPK = Peak output current = 40mA
The maximum value of RLIM is set by VIN(MIN), VOUT(MAX) and
the dropout voltage (see transf er characteristic on page 3) of
the ZXCT1009 :-
RLIM(MAX) = ROUT[VIN(MIN) – (VDP + VOUT(MAX))]/VOUT(MAX)
VIN(MIN) = Minimum Supply Operating Voltage
VDP = Dropout Voltage
VOUT(MAX) = Maximum Operating Output Voltage
V
IN
R
SENSE
To load
V
OUT
R
OUT
1
23
ZXCT1009
V
SENSE+
V
SENSE-
I
OUT
R
LIM
V
IN
R
SENSE
To load
V
OUT
R
OUT
1
23
ZXCT1009
V
SENSE+
V
SENSE-
I
OUT
R
LIM
ZXCT1009
HIGH-SIDE CURRENT MONITOR
ZXCT1009
Document number: DS33441 Rev. 12 - 2 6 of 8
www.diodes.com April 2011
© Diodes Incorporated
Application Information (cont.)
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 sho ws
the linear rise in voltage across the resistor due to the PTC of
the material and demonstrates ho w this rise in resistance value
over temperature compensates for the NTCof the device.
The figure opposite shows a PCB layout suggestion. The
resistor section is 25mm x 0.25mm giving approximately 150m
using 1oz copper. The data for the normalised graph was
obtained using a 1A load current and a 100 output resistor. An
electronic version of the PCB layout is available thr ough Diodes
applications group.
Effect of Sense Resisitor Material
on Temperature Performance
Layout shows area of shunt resistor compared to SOT23
package. Not actual size.
Ordering Information
Device AEC-Q100
level Reel
Size Tape Width Quantity per Reel Part Marking Package
ZXCT1009FTA Grade 3 7” 8mm 3000 Units 109 SOT23
ZXCT1009F-7 None 7” 8mm 3000 Units 109 SOT23
ZXCT1009T8TA None 7” 12mm 1000 Units ZXCT1009 SM8
ZXCT1009
HIGH-SIDE CURRENT MONITOR
ZXCT1009
Document number: DS33441 Rev. 12 - 2 7 of 8
www.diodes.com April 2011
© Diodes Incorporated
Package Outline Dimensions (All Dimensions in mm)
1) SOT23
2) SM8
SOT23
Dim Min Max Typ
A 0.37 0.51 0.40
B 1.20 1.40 1.30
C 2.30 2.50 2.40
D 0.89 1.03 0.915
F 0.45 0.60 0.535
G 1.78 2.05 1.83
H 2.80 3.00 2.90
J 0.013 0.10 0.05
K 0.903 1.10 1.00
K1 - - 0.400
L 0.45 0.61 0.55
M 0.085 0.18 0.11
α 0° 8° -
All Dimensions in mm
SM-8
Dim Min Max Typ
A − 1.7 −
A1 0.02 0.1 −
b − 0.7 −
c 0.24 0.32 −
D 6.3 6.7 −
e − − 1.53
e1 − − 4.59
E 6.7 7.3 −
E1 3.3 3.7 −
L 0.9 − −
All Dimensions in mm
15° 45°
L
c
E1
E
D
b
ee1
AA1
A
M
JL
D
F
BC
H
K
G
K1
ZXCT1009
HIGH-SIDE CURRENT MONITOR
ZXCT1009
Document number: DS33441 Rev. 12 - 2 8 of 8
www.diodes.com April 2011
© Diodes Incorporated
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