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ZXCT1009
HIGH-SIDE CURRENT MONITOR
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 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. 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 4 A, combined with its SOT23 package make it a unique solution for portable battery equipment.
APPLICATIONS
* Battery chargers * Smart battery packs * DC motor control * Over current monitor * Power management * Level translating * Programmable current source
APPLICATION CIRCUIT
FEATURES
* Low cost, accurate high-side current sensing * Output voltage scaling * Up to 2.5V sense voltage * 2.5V - 20V supply range * 4A quiescent current * 1% typical accuracy * SOT23 and SM8 packages
ORDERING INFORMATION
DEVICE
ZXCT1009FTA ZXCT1009T8TA
REEL SIZE
7" 7"
TAPE WIDTH
8mm 12mm
QUANTITY PER REEL
3,000 units 1,000 units
PARTMARKING
109 ZXCT1009
PACKAGE
SOT23 SM8
ISSUE 10 - JULY 2007 1
SEMICONDUCTORS
ZXCT1009
ABSOLUTE MAXIMUM RATINGS
Voltage on any pin Continuous output current, IOUT, Continuous sense voltage, VSENSE, Operating temperature, TA, Storage temperature Package power dissipation SOT23 SM8 -0.6V to 20V (relative to Iout) 25mA -0.5V to +5V -40 to 85C -55 to 125C (TA = 25C) 450mW - derate to zero at 125C 2W
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 = 25C, Vin = 5V, Rout = 100. SYMBOL
V in I out 1
PARAMETER
V CC range Output current V SENSE =0V
CONDITIONS Min.
2.5 1 90 0.975 1.95 9.6 0
LIMITS Typ.
4 104 1.002 2.0 9.98
UNIT Max.
20 15 120 1.025 2.05 10.2 2500 100 V A A mA mA mA mV nA
V SENSE =10mV V SENSE =100mV V SENSE =200mV V SENSE =1V V sense I sense Acc Gm Sense voltage V sense input current Accuracy Transconducta nce, I out / V sense Bandwidth VSENSE(DC) = 10mV, Pin = -40dBm VSENSE(DC) = 100mV, Pin = -20dBm
1 Includes input offset voltage contribution VSENSE is defined as the differential voltage VSENSE = VSENSE+ - VSENSE= VIN - VLOAD = ILOAD x RSENSE
R SENSE = 0.1 V SENSE =200mV -2.5 10000 0 300 2 2.5 % A/V
BW
kHz MHz
between VSENSE+ and VSENSE-.
-20dBm=63mVp-p into 50
ISSUE 10 - JULY 2007
SEMICONDUCTORS
2
ZXCT1009
TYPICAL CHARACTERISTICS
5 10m
IOUT - Output Current (A)
Output Current Error (%)
1m
VIN = 5V Tamb = 25C ROUT = 0W
4 3 2 1 0 -1 -2 10m 100m
Typical
VIN = 5V Tamb = 25C ROUT = 0W
100
10 100 1m 10m 100m 1
1
VSENSE (V)
VSENSE (V)
Typical Output v Sense Voltage
3 10.2
VIN = 5V VSENSE = 1V ROUT = 0W
Error v Sense Voltage
IOUT - Output Current (mA)
VIN = 5V, Tamb = 25C, RF PIN = -20dBm
0 -3
DC VSENSE = 0.01V
10.0
9.8
Gain (dB)
-6 -9 -12 0.01
DC VSENSE = 0.1V DC VSENSE = 1V
9.6
9.4 -40
-20
0
20
40
60
80
0.1
1
10
Temperature (C)
Frequency (MHz)
Output Current v Temperature
12 0
VIN = 5V Tamb = 25C ROUT = 0W VSENSE = 1V VSENSE = 0.8V VSENSE = 0.6V VSENSE = 0.4V VSENSE = 0.2V
Frequency Response
IOUT - Output Current (mA)
-10 -20
10 8 6 4 2 0 0
VIN = 5V Tamb = 25C RF PIN = -20dBm
VSENSE = 1V
Rejection (dB)
-30 -40 -50 -60 -70 -80 -90
VSENSE = 0.1V VSENSE = 0.01V
1
2
3
4
5
1
10
100
1k
10k
100k
1M
10M
VIN - Supply Voltage (V)
Frequency (Hz)
Transfer Characteristic
ISSUE 10 - JULY 2007 3
Common Mode Rejection
SEMICONDUCTORS
ZXCT1009
TYPICAL CHARACTERISTICS (Cont.) SCHEMATIC DIAGRAM
PIN DESCRIPTION
Pin Name V sense+ V senseI out Pin Function Supply voltage Connection to load/battery Output current, proportional to V in -V load
CONNECTION DIAGRAMS SOT23 Package Suffix - F SM8 Package Suffix - T8
Top View
Top View
ISSUE 10 - JULY 2007
SEMICONDUCTORS
4
ZXCT1009
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 temperature (Tjmax), and ambient temperature (Tamb), according to the expression: Pmax = (Tjmax - Tamb) / ja E.g. The device power dissipation, PD is given by the expression: PD=Iout.(Vin-Vout) Watts 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 ohms. 2)Choose Rout to give Vout = 100mV, when Vsense = 100mV. Rearranging 1 for Rout gives: Rout = Vout /(Vsense x 0.01)
SM8
APPLICATIONS INFORMATION The following lines describe how to scale a load current to an output voltage. Vsense = Vin - Vload Vout = 0.01 x Vsense x Rout1
A 1A current is to be represented by a 100mV output voltage:
Rout = 0.1 / (0.1 x 0.01) = 100
SOT23
TYPICAL CIRCUIT APPLICATION
Where Rload represents any load including DC motors, a charging battery or further circuitry that requires monitoring, R sense can be selected on specific requirements of accuracy, size and power rating.
ISSUE 10 - JULY 2007 5
SEMICONDUCTORS
ZXCT1009
APPLICATIONS INFORMATION (Continued)
Charger input FMMT3904 FZT789A ZHCS100 Vin FMMD914 5V Load To battery +
Transient Protection
An additional resistor, Rlim can be added in series with Rout (figure 1.0), 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.
bq2954
MOD pin
FMMT451 Iout
ZXCT1009
SNS pin
Support components omitted for clarity
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 Zetex FZT789A high current Super- 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. 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.
Figure 1.0 ZXCT1009 with additional current limiting Resistor Rlim. Assuming 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 transfer 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
ISSUE 10 - JULY 2007
SEMICONDUCTORS
6
APPLICATIONS INFORMATION (Continued)
ZXCT1009
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 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 at www.zetex.com/isense.
ZXCT1009 Vout Vin
Rout
ZXCT1009 Vout Vin
Load
GND
Actual Size
Load GND
Layout shows area of shunt resistor compared to SOT23 package. Not actual size
1.4
Normalised Voltage
Voltage across Copper Sense Resistor
1.2
VOUT with Copper Sense Resistor
1.0
VOUT with Ideal Sense Resistor
0.8 -40 -20 0 20
40
60
80
100 120 140
Temperature (C)
Effect of Sense Resistor Material on Temperature Performance
ISSUE 10 - JULY 2007 7
SEMICONDUCTORS
Rout
ZXCT1009
Definitions Product change Zetex Semiconductors reserves the right to alter, without notice, specifications, design, price or conditions of supply of any product or service. Customers are solely responsible for obtaining the latest relevant information before placing orders. Applications disclaimer The circuits in this design/application note are offered as design ideas. It is the responsibility of the user to ensure that the circuit is fit for the user's application and meets with the user's requirements. No representation or warranty is given and no liability whatsoever is assumed by Zetex with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or otherwise. Zetex does not assume any legal responsibility or will not be held legally liable (whether in contract, tort (including negligence), breach of statutory duty, restriction or otherwise) for any damages, loss of profit, business, contract, opportunity or consequential loss in the use of these circuit applications, under any circumstances. Life support Zetex 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 Zetex Semiconductors plc. As used herein: 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 instructions for use 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 to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. Reproduction The product specifications contained in this publication are 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 contract or be regarded as a representation relating to the products or services concerned. Terms and Conditions All products are sold subjects to Zetex' terms and conditions of sale, and this disclaimer (save in the event of a conflict between the two when the terms of the contract shall prevail) according to region, supplied at the time of order acknowledgement. For the latest information on technology, delivery terms and conditions and prices, please contact your nearest Zetex sales office. Quality of product Zetex is an ISO 9001 and TS16949 certified semiconductor manufacturer. To ensure quality of service and products we strongly advise the purchase of parts directly from Zetex Semiconductors or one of our regionally authorized distributors. For a complete listing of authorized distributors please visit: www.zetex.com/salesnetwork Zetex Semiconductors does not warrant or accept any liability whatsoever in respect of any parts purchased through unauthorized sales channels. ESD (Electrostatic discharge) Semiconductor devices are susceptible to damage by ESD. Suitable precautions should be taken when handling and transporting devices. The possible damage to devices depends on the circumstances of the handling and transporting, and the nature of the device. The extent of damage can vary from immediate functional or parametric malfunction to degradation of function or performance in use over time. Devices suspected of being affected should be replaced. Green compliance Zetex Semiconductors is committed to environmental excellence in all aspects of its operations which includes meeting or exceeding regulatory requirements with respect to the use of hazardous substances. Numerous successful programs have been implemented to reduce the use of hazardous substances and/or emissions. All Zetex components are compliant with the RoHS directive, and through this it is supporting its customers in their compliance with WEEE and ELV directives. Product status key: "Preview"Future device intended for production at some point. Samples may be available "Active"Product status recommended for new designs "Last time buy (LTB)"Device will be discontinued and last time buy period and delivery is in effect "Not recommended for new designs"Device is still in production to support existing designs and production "Obsolete"Production has been discontinued Datasheet status key: "Draft version"This term denotes a very early datasheet version and contains highly provisional information, which may change in any manner without notice. "Provisional version"This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance. However, changes to the test conditions and specifications may occur, at any time and without notice. "Issue"This term denotes an issued datasheet containing finalized specifications. However, changes to specifications may occur, at any time and without notice.
ISSUE 10 - JULY 2007
SEMICONDUCTORS
8
PACKAGE DIMENSIONS SOT23
DIM Millimeters Min A
N
ZXCT1009
Inches Min 0.105 0.047 - 0.0145 0.0033 Max 0.120 0.055 0.043 0.021 0.0059 Max 3.05 1.40 1.10 0.53 0.15 NOM 1.9 0.01 2.10 0.10 2.50
NOM 0.95
2.67 1.20 - 0.37 0.085
B C D F G K L N
NOM 0.075 0.0004 0.0825 0.004 0.0985
NOM 0.037
PACKAGE DIMENSIONS SM8
DIM Min A A1 b c D E e1 e2 He Lp - 0.02 - 0.24 6.3 3.3 - - 6.7 0.9 - - Millimeters Typ - - 0.7 - - - 4.59 1.53 - - - 10 Max 1.7 0.1 - 0.32 6.7 3.7 - - 7.3 - 15 - Min - 0.0008 - 0.009 0.248 0.130 - - 0.264 0.035 - - Inches Typ - - 0.028 - - - 0.180 0.060 - - - 10 Max 0.067 0.004 - 0.013 0.264 0.145 - - 0.287 - 15 -
(c) Zetex Semiconductors plc 2007
Europe Zetex GmbH Kustermann-Park Balanstrae 59 D-81541 Munchen Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 europe.sales@zetex.com Americas Zetex Inc 700 Veterans Memorial Hwy Hauppauge, NY 11788 USA Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 usa.sales@zetex.com Asia Pacific Zetex (Asia) Ltd 3701-04 Metroplaza Tower 1 Hing Fong Road, Kwai Fong Hong Kong Telephone: (852) 26100 611 Fax: (852) 24250 494 asia.sales@zetex.com Corporate Headquarters Zetex Semiconductors plc Zetex Technology Park Chadderton, Oldham, OL9 9LL United Kingdom Telephone (44) 161 622 4444 Fax: (44) 161 622 4446 hq@zetex.com
ISSUE 10 - JULY 2007 9
SEMICONDUCTORS

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