DIODES ZXCT1011

ZXCT1011
High-side low drift current monitor
Description
The ZXCT1011 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 ZXCT1011 takes the voltage developed across a current shunt resistor and translates it into a
proportional output current.
A user defined output resistor scales the output current into a ground referenced voltage.
A current reference resistor, external to the IC, results in an improved temperature coefficient
compared to the ZXCT1009.
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 4uA, combined with its SOT23-5 package
make it suitable for portable battery equipment too.
Features
Applications
■ Accurate high-side current sensing
■ Automotive current measurement
■ 2.5V to 20V supply range
■ Battery management
■ 4 µA quiescent current
■ DC motor and solenoid control
■ 1% typical accuracy
■ Over current monitor
■ Package SOT23-5
■ Power management
■ Temperature range -40 to 125°C
Typical application circuit
R sense
Vin
Pin connections
Load
N/C
Rshunt
120 Ω
Vsense+
3
Vsense+
4
5
Iout
Vsense-
ZXCT1011
Rshunt
Vsense-
I out
2
V
Rout
GND
Ordering information
Order code
Pack
Part
mark
Reel Size
inches (mm)
Tape width
Quantity Per
reel
ZXCT1011E5TA
SOT23-5
1011
7 (180)
8mm
3,000
Issue 1- July 2005
© Zetex Semiconductors plc 2005
1
www.zetex.com
ZXCT1011
Absolute maximum ratings
Vsense+
20 V
Voltage on any pin
0.6V and Vsense+ +0.5V
Vsense+ to Vsense-
2.5V
Operating temperature
-40 to 125°C
Storage temperature
-55 to 150°C
Maximum junction temperature
150°C
Package power dissipation
300mW at TA = 25°C (De-rate to zero at 150°C)
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
Test conditions TA = 25°C, Vin = 5V, Rshunt = 120⍀. Vsense=100mV. Unless otherwise stated.
Symbol Parameter
Conditions
Min
Typ.
Max
Units
Supply range
-
2.5
-
20
V
Iout
Output current
Vsense
1
84
273
0.97
1.95
4.85
4
116
320
1.00
2.00
5.00
15
124
330
1.03
2.05
5.15
µA
µA
µA
mA
mA
mA
Vsense
Sense voltage†
-
0
-
500
mV
Isense -
Vsense- input current
-
-
-
100
nA
Acc
Accuracy
Rsense = 0.1⍀
Vsense = 100mV
-3
-
3
%
gm
Transconductance
Iout/Vsense
Rshunt = 120⍀
-
10
-
mA/V
Tc
Temperature coefficient‡ -
-
30
150
ppm/° C
BW**
Bandwidth
Vsense = 10mV
CL = 5pF, Rout = 1k⍀
Vsense = 100mV
CL = 5pF, Rout = 1k⍀
-
400
-
kHz
Vsense = 200mV, Rout=1k⍀
-
Vin*
PSSR
Supply rejection
= 0V
=10mV
=30mV
=100mV
=200mV
=500mV
1.5
68
MHz
-
dB
NOTES:
* Vsense+ relative to Iout.
† Vsense = (Vsense+) - (Vsense-).
‡ Temperature dependent measurements are extracted from characterization and simulation results.
** Where CL is the capacitance across Rout.
Issue 1- July 2005
© Zetex Semiconductors plc 2005
2
www.zetex.com
ZXCT1011
Typical characteristics
TA=25°C, Rshunt = 120
Issue 1- July 2005
© Zetex Semiconductors plc 2005
unless otherwise stated.
3
www.zetex.com
ZXCT1011
Typical characteristics
TA=25°C, Rshunt = 120
Issue 1- July 2005
© Zetex Semiconductors plc 2005
unless otherwise stated.
4
www.zetex.com
ZXCT1011
Pin description
Pin no.
Pin name
Pin function
1
N/C
No connection
2
Iout
Output current - follows transconductance of sense voltage gm = 10mA/V
for Rshunt=120⍀
3
Rshunt
Trimming resistor Input. - used to trim gain value 60⍀ ⱕ Rshunt ⱕ 240⍀
4
Vsense-
Low side current sense input. – connect to load/battery etc. Must be
lower than Vsense+ for correct operation. Cannot be grounded
without additional series resistor.
5
Vsense+
High side current sense input. – Connect to supply rail. Must be
higher than Vsense+ for correct operation.
Application information
Design example
The following lines describe how to scale a load current to an output voltage.
Vsense = (Vsense+) - (Vsense-) = Iload x Rsense
Defining then
Iout = Iq + Vsense x gm
since
gm= 1.2 / Rshunt
Iout
= Iq + [ (Vsense x 1.2) / Rshunt ]
= Iq + [ (1.2 x Iload x Rsense / Rshunt) ]
Note: Iq is embedded into the specification of the ZXCT1011 and therefore appears an offset error.
∴Vout = (Rout x Ioffset) + [(1.2 x Rout x Iload x Rsense) / Rshunt]
The output current of the ZXCT1011 is directly related to the size of the trimming resistor used. It
is important to ensure the tolerance of Rshunt is considered. A 1% change in Rshunt will cause a
1% change in output.
Consider the following: -
Issue 1- July 2005
© Zetex Semiconductors plc 2005
5
www.zetex.com
ZXCT1011
A 1 ampere load current is to be measured into a battery. The output signal required to an over
current controller needs to be 3.3V. What is a suitable value of Rout and what will the error due
to the supply current be?
Vin = 5.0V - 9.0V
Iload = 1.0A
Output signal required: 3.3V
Vin = 5.0V - 9.0V
R sense
Rshunt
120R
5
Vsense+
3
Iload = 1A
4
V sense-
ZXCT
R shunt
1011
I out
R load
2
3.3V
R out
Figure 1
ZXCT1011 to measure a 1.0 A load current
To obtain the highest accuracy, choose the of Rsense to give 100mV:
Rsense = 0.1/1.0 = 0.1⍀
The transconductance using a 120⍀ resistor will be 10mA/V.
Choose Rout to give Vout = 3.3V, when Vsense = 100mV
Rearranging equation 1 without the offset error gives:
Rout = (Vout x Rshunt) / (1.2 x ILoad x Rsense)
Rout = 3.3k⍀
Now consider the offset error for this resistor:
Offset due to supply current = Rout x 4x10-6µA = 13.2mV = 0.4%
Issue 1- July 2005
© Zetex Semiconductors plc 2005
6
www.zetex.com
ZXCT1011
Application information (cont.)
Minimum operating voltage
The minimum operating voltage of the ZXCT1011 is 2.5V and is defined as the difference between
Vsense+ and the Iout pin. It must be ensured that sufficient headroom is given for the operation of
the device when considering Rout.
R sense
Vin = 10V
Rshunt
120R
5
4
V sense-
V sense+
3
R shunt
To load
ZXCT
1011
I out
R
2
Vout
3.3K
Figure 2
Considerations for supply rail
Voltage across device 2.5V
Vin - Vout 2.5V
Where Vout = Iout x Rout
At low supply voltages and high Vsense measurements, special care must be taken to ensure the
correct operation.
The circuit in figure 2.0 shows a ZXCT1011 operating from 10V supply rail. The minimum
operating voltage of the ZXCT1011 is 2.5V. This allows a maximum output voltage of 7.5V to be
set at Vout. A 3k resistor on the output would draw a maximum 2.5mA from Iout. - See minimum
usable supply voltage graph on page 4.
Issue 1- July 2005
© Zetex Semiconductors plc 2005
7
www.zetex.com
ZXCT1011
Packaging details - SOT23-5
Europe
Americas
Asia Pacific
Corporate Headquarters
Zetex GmbH
Streitfeldstraße 19
D-81673 München
Germany
Zetex Inc
700 Veterans Memorial Highway
Hauppauge, NY 11788
USA
Zetex (Asia Ltd)
3701-04 Metroplaza Tower 1
Hing Fong Road, Kwai Fong
Hong Kong
Zetex Semiconductors plc
Zetex Technology Park, Chadderton
Oldham, OL9 9LL
United Kingdom
Telefon: (49) 89 45 49 49 0
Fax: (49) 89 45 49 49 49
europe.sales@zetex.com
Telephone: (1) 631 360 2222
Fax: (1) 631 360 8222
usa.sales@zetex.com
Telephone: (852) 26100 611
Fax: (852) 24250 494
asia.sales@zetex.com
Telephone (44) 161 622 4444
Fax: (44) 161 622 4446
hq@zetex.com
These offices are supported by agents and distributors in major countries world-wide.
This publication is 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 contact or be regarded as a representation relating to the products or services
concerned. The company reserves the right to alter without notice the specification, design, price or conditions of supply of any product or
service.
Issue 1- July 2005
© Zetex Semiconductors plc 2005
8
www.zetex.com