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ZXCT1012 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 TSOT23-5, and TDFN3x3-5. A minimum operating current of just 3.5A, combined with its TSOT23-5 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.
Features
* * * * * 2.5V to 20V supply range 3.5A quiescent current Current output - user set gain Thin package - TSOT23-5 and TDFN3x3-5 Temperature range -40 to 85C
Applications
* * * * Battery fuel gauge Battery chargers Overcurrent monitor Power management
Pin connections
SENSE-
Applications circuit
IN SENSE
OUT
TSOT23-5 Pinout - top view
SENSE+
SENSE+ SENSE-
ZXCT1012
OUT
LOAD OUT
NC GND OUT
3
4
SENSE-
2
1
5
SENSE+
OUT
TDFN3x3-5 Pinout - bottom view
Ordering information
Device Package Status Active Active Device marking 1012 1012 Reel size Tape width (inches) (mm) 7 7 8 8 Quantity per reel 3000 3000
ZXCT1012DAATA TDFN-5 (3mm x 3mm) ZXCT1012ET5TA TSOT23-5
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ZXCT1012
Pin information
Pin TDFN5 TSOT23-5 3 2 1 1 2 3 N/C GND OUT No connection Ground connection Output current pin. Current generated due to a difference voltage between VSENSE+ and VSENSE- flows out of this pin. A suitable value resistor connected to ground creates an output voltage. The maximum voltage out of this pin will be VSENSE- - 1.5V. Name Description
5
4
SENSE+ 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. SENSE- This is the negative input of the current monitor and has an input range from 20V down to 2.5V.
4
5
Absolute maximum ratings
VSENSE+ max. Voltage on any pin (relative to GND pin) VSENSE() Ambient operating temperature range Storage temperature Maximimum junction temperature Package power dissipation Package TSOT23-5 (*) TDFN3x3 5 pin(*) () R JA 250C/W 232C/W 20V -0.6 and VSENSE+ +0.5V -0.15V to +3V -40 to 85C -55 to 150C 150C 300mW at Tamb= 25C (De-rate to zero at 150C) PDISS at 25C 500mW 540mW
NOTES: (*) Mounted on 30mm x 16mm x1.1mm FR4 board with 1oz copper.
Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability.
NOTES: () VSENSE is defined as the differential voltage between the SENSE+ and SENSE- pins. VSENSE = VSENSE+ - VSENSE() Exposed lead not connected to thermal plane
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ZXCT1012
Recommended operating conditions
Symbol VIN TA VSENSE VOUT Recommended parameter Sense+ range Ambient temperature range differential Sense voltage Output voltage swing Min. 2.5 -40 10 0 Limits Max. 20 85 2500 VSENSE- -1.5
Units V C mV V
Electrical characteristics Test conditions Tamb = 25C, VIN = VSENSE+ = 5V, unless otherwise stated
Symbol Parameter IOUT Output current Conditions VSENSE = 0V VSENSE = 10mV VSENSE = 40mV VSENSE = 100mV VSENSE = 200mV IQ ISENSEAcc Gm Tc BW Ground pin current VSENSE = 0V SENSE- pin input current Accuracy Transconductance, IOUT/VSENSE(*) Temperature coefficient Bandwidth VSENSE = 200mV Tamb = 0 to 50C CL = 5pF, ROUT = 1k
(*)
Min. 0 85 380 0.975 1.95
Limits Typ. 0.3 100 400 1.00 2.00 3.5
Unit Max. 15 115 420 2.05 8 100 A A A mA A nA % mA/V ppm/ C kHz MHz dB
1.025 mA
RSENSE = 0.1V VSENSE = 200mV
-2.5 10 500 300 2 80
2.5
VSENSE = 10mV VSENSE = 100mV
CMRR() Common mode rejection ratio
VSENSE = 100mV, ROUT = 1k VIN = 2.5V to 20V
NOTES: (*) Temperature dependent measurements are extracted from characterisation and simulation results. () With the ZXCT1012 using SENSE+ as its power supply pin, common mode rejection cannot be distinguished from power supply rejection.
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ZXCT1012
Typical characteristics
2% 0% -2% -4%
-6%
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ZXCT1012
Applications information
The ZXCT1012 current monitor works by converting the voltage developed across a small sense resistor into a current on the out pin. In reality it is a voltage to current converter. This output current can be converted into a voltage simply by passing it through a resistor (ROUT) to ground. The current monitor has a transconductance of 10mA/V. But the overall amplifying conversion is affected by both the RSENSE and ROUT. The gain equation of the ZXCT1012 is: R OUT V OUT = I L x R SENSE -------------100 For best performance RSENSE should be connected as close to the SENSE+ (and SENSE-) pins; which minimizes any series resistance with RSENSE and potential for interference pickup. When choosing appropriate values for RSENSE a compromise must be reached between in-line signal loss (including potential power dissipation effects) and small signal accuracy. Higher values for RSENSE gives better accuracy at low load currents by reducing the inaccuracies due to internal offsets. For best operation the ZXCT1012 has been designed to provide best performance with VSENSE of the order of 40mV to 200mV. Current monitors are single supply devices which means they tend to saturate at very 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. Zetex has specified the output voltage at VSENSE of 10mV, 40mV, 100mV and 200mV; which is the recommended sense voltage range. The maximum differential input voltage, VSENSE, is 2.5V; however this will cause large output currents to flow increasing power dissipation in the chip. The sense voltage can be increased further, without damaging the ZXCT1012, by the inclusion of a resistor, RLIM, between SENSE- pin and the load. Typical values around 10k . See figure below.
SENSE
RLIM CC
ZXCT1012
If large reverse currents are expected then the resistor, RLIM, will provide protection from exceeding absolute maximum ratings. A suitable value for RLIM can be determined from: V SENSE ( REF R LIM ----------------------------------) 5mA Where VSENSE(REV) is the maximum expected reverse sense voltage generated.
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ZXCT1012
The following lines describe how to scale a load current to an output voltage. VSENSE IOUT VOUT = RSENSE * ILOAD = 10mA/V x VSENSE = IOUT x ROUT equation (1) equation (2) equation (3)
Design example
In the circuit below a 1A current is to be represented by a 100mV output voltage (VOUT): A) To be within recommended values choose the value of RSENSE to give: 50mV > VSENSE > 200mV at full load. For example set VSENSE = 100mV at 1.0A. From equation (1) RSENSE = 0.1V/1.0A = 0.1
B) Now choose ROUT to give: VOUT = 100mV, when VSENSE = 100mV. From equation (2) IOUT ROUT = VOUT/IOUT
IN SENSE
= 10mA/V x 0.1
= 1mA
Rearranging equation (3) for ROUT gives: = 0.1/0.001 = 100
SENSE+
SENSE-
ZXCT1012
GND OUT
LOAD OUT
OUT
= 0.1 / (0.1 x 0.01) = 100
Typical circuit application
Where RLOAD represents 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.
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ZXCT1012
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
The device power dissipation, PD is given by the expression: PD=IOUT.(VIN-VOUT) watts Care must be taken when using this device at large input voltages and large sense voltages to prevent too much power dissipation.
Power Dissipation
TDFN3x3-5 TSOT23-5
600
PD - Power Dissipation (mW)
500 400 300 200 100 0
0
25
50
75
100
125
150
TA - Ambient temperature (C)
VIN ROUT IOUT
= 20V = 100 = 2.5 x 0.01 = 25mA
VSENSE = 2.5V
VOUT
= IOUT x ROUT = 25mA x 100 = 2.5V
PD
= 25mA (20 - 2.5)V = 438mW
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ZXCT1012
Package outline - TSOT23-5
DIM A A1 A2 b c D E E1 e e1 L L2 a Min. 0.01 0.84 0.30 0.12
Millimeters Max. 1.00 0.10 0.90 0.45 0.20 2.90 BSC 2.80 BSC 1.60 BSC 0.95 BSC 1.90 BSC 0.30 0.25 BSC 4 12 4 0.50 0.0118 Min. 0.0003 0.0330 0.0118 0.0047
Inches Max. 0.0393 0.0039 0.0354 0.0177 0.0078 0.114 BSC 0.110 BSC 0.062 BSC 0.0374 BSC 0.0748 BSC 0.0196 0.010 BSC 12
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
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ZXCT1012
DAA package outline - TDFN3x3-5
E
A A3
L
E2 E2/2
K
D2/2
Dim. e E E2 L K Millimeters Min. Max. 0.95REF 3.00BSC 0.85 0.30 0.20 1.10 0.50 -
e
Dim. A A1 A3 b D D2
Millimeters Min. 0.70 0.00 Max. 0.80 0.05
Inches Min. 0.0276 0.00 Max. 0.0315 0.002
b
A1
Inches Max. Max. 0.0374REF 0.1181BSC 0.0335 0.0118 0.0079 0.0433 0.0197 -
0.20REF 0.30 1.85 0.45 2.10
0.0079REF 0.0118 0.0728 0.0177 0.0827
3.00BSC
0.1181BSC
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
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D
ZXCT1012
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 labelling 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. Zetex sales offices 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 Highway 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
(c) 2006 Published by Zetex Semiconductors plc
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