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ZXCT1032 High-side inrush controller and electronic fuse
Description
The ZXCT1032 is a high-side current monitor that drives a PMOS or PNP transistor to provide in-rush current limit and over-current protection. The ZXCT1032 includes a high accuracy high-side current monitor, a start-up timer and a re-try inhibit timer. The ZXCT1032 takes the voltage developed across a current shunt resistor and compares this with an externally set trip point. It works in three modes: * * * Linear soft-start Over-current detector Over-current disconnect/fuse While in this mode the internal current monitor continually checks the output current and compares it to the trip-current level determined by VISET.
Over-current disconnect/fuse
If the trip current limit is exceeded at any time the ZXCT1032 enters its Over-current disconnect mode. The drive pin is driven high, turning the pass MOSFET off; the flag output goes low indicating a fault. The drive and flag outputs are latched in these states for a period determined by CT, VISET and the internally set discharge current (3A typical). After CT has discharged to 80mV the ZXCT1032 will restart into its linear soft-start mode. The CT charge and discharge times have been ratioed to so that the power dissipation in the pass MOSFET should allow indefinite operation in the event of a continuous load failure.
Linear soft-start
Upon power up the ZXCT1032 enters a linear soft-start mode. During which the output current ramps up from zero to a maximum user defined trip point. The trip point is set by the voltage on ISET pin and RSENSE. The ramp rate is determined by capacitor CT. The soft start ensures that capacitive loads are smoothly charged without causing excessive power supply startup transients.
Pin 3 description:
Determines the load current trip level or constant current level. ISET can be left open circuit (internal 2.1V reference) or driven via a DC voltage or C PWM output. Its source impedance is 50k .
Over-current detectior
When external capacitor CT has charged up above the VISET the ZXCT1032 switches from its soft-start mode to its over-current detection mode. During this mode the external MOSFET will be fully enhanced reducing the its voltage drop and power dissipation.
Features
* * * * * * * Accurate high-side current sensing User defined and dynamically adjustable trip current Load switch control Fault flag logic output User defined ramp and inhibit timers SO8 package Temperature range -40 to 85C
Applications
* * * * Electronic fuse Short circuit protected supply feed Hot swap Power over twisted pair
Ordering information
Order code ZXCT1032N8TA Issue 3 - April 2007
(c) Zetex Semiconductors plc 2007
Pack SO8
Part mark 1032
Reel size 7" 1
Tape width 12mm
Quantity per reel 500 www.zetex.com
ZXCT1032
Typical application circuit
VIN R SENSE 8 IN+ ISET GND 1 6 INDrive 5 Load Flag 4 CT GND C
GNDCT ISET Flag
1
Pinout connections
SO8
8
IN+ N/C INDrive
2
7
3
6
3
ZXCT 1032 CT
2
4
5
Top view
Pin description
Pin 1 2 Name GND CT Description Ground reference for ISET and Flag pins. Most negative terminal of the device. No other pin should go below this voltage. An external capacitor is connected to this pin and is used to determine the period for constant-current mode and the timeout before restarting. To reduce excessive heating during the soft start mode capacitors less than 220nF are reocmmended. Determines the load current trip level or constant current level. This can be driven via a DC voltage or via a C PWM output. VSENSE = (VISET-150mV)/10 An input <100mV will disable the high-side switch (i.e. set IOUT = 0) If left open-circuit, an accurate internal DC reference of 2.1V and source impedance of 50k is used to set the voltage on this pin. (External drivers must take this reference into account.) 4 Flag This is an active low open collector output that goes low whenever the current limit set by the choice of RSENSE and ISET is reached or in the event of a shorted load. This is the output drive pin to the external high side referred switch on the ZXCT1032, capable of driving PMOS and PNP transistors. The load referred input to the current monitor control loop. Not connected Acts as both the supply pin to the ZXCT1032 and the supply referred sense input to the current monitor control loop.
3
ISET
5 6 7 8
Drive INN/C IN+
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ZXCT1032
Absolute maximum ratings
VIN+ max(a) ...................................................................................................... 28 V Voltage on any pin relative to GND ............................................................. -0.6V and VIN +0.5 V Maximum differential voltage between VIN+ and VIN- (VSENSE) ................ 500 mV Junction temperature range ........................................................................ -40 to 150C Storage temperature range .......................................................................... -55 to 150C Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability.
NOTES: (a) Up to a maximum of 24 hours
Recommended operating conditions
Symbol VIN+ TA VFLAG VISET Parameter Supply range Ambient temperature range Flag voltage range Voltage on ISET pin Min. 9.5 -40 0 1 Max. 21 85 VIN+ 2.5 Units V C V V
Electrical characteristics
Test conditions Tamb = 25C, VIN+ = 20V. Unless otherwise stated. Symbol Parameter IQ Quiescent current VSTRIP
(*)
Conditions VSENSE1 = 0V, V_ISET = 2.1V VISET =1.1V VISET =2.1V IISET = 0 VISET =0V VISET = 2.1V, VSENSE > 205mV, IDRIVE = 0,
Min.
Typ. 1.6 95 195 2.1 45 VIN- 0.2 VIN- 5.5 9 0.2 1 100 95
Max. Units 2.5 mA mV 205 2.2 60 V A V VIN- 4 0.4 200 200 V k V nA nA ppm/C 270 5.4 A A
Flag trip threshold voltage ISET open voltage ISET output current
185 2.0 30 VIN- 0.4 VIN-7
VISET IISET
VDRIVEH Drive high output voltage
VDRIVEL Drive low output voltage VISET = 2.1V, VSENSE < 185mV, IDRIVE = 0, RDRIVEL Drive low output resistance VISET = 2.1V, VSENSE < 185mV VFLAGL Flag Low output Voltage VISET = 2.1V, VSENSE > 205mV IFLAG = 100A IFLAGZ Flag open circuit leakage VISET = 2.1V, VSENSE < 185mV, current VFLAG = 5V IININ- bias current VISET = 0V VSTRIP-TC Temperature coefficient See footnote () of trip voltage ICT-CHG Capacitor CT charging FLAG = Open current ICT-DIS Capacitor CT discharging FLAG = Low current
130 1.8
200 3.3
NOTES: (*) VSENSE = VIN+ - VIN-. VSTRIP is the sense voltage at which the device trips into over-current protection. () Temperature dependent measurements are extracted from characterization and simulation results.
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ZXCT1032
Typical characteristics (TA = 25C and VIN+ = 20V unless otherwise stated)
Quiescent current vs temperature
0.90
VIN+ = 9.5 to 21V
Quiescent current vs input voltage
0.80
0.60 IQ (mA)
0.79 IQ (mA)
0.30
0.78
0.00 -40
-15
10 35 Temperature (C)
60
85
0.77
9
11
13
15 Input voltage
17
19
21
VISET vs temperature
2.20
VIN+ = 9.5 to 21V
VISET vs input voltage
2.101
T A = 25C
2.15 VISET (V)
2.10
2.05
2.00 -40
-15
10 35 Temperature (C)
60
85
VISET (V) 2.100 2.099 9 10 11 12 13 14 15 16 17 Input voltage (V) 18 19 20 21
IIN- vs temperature
50
VIN+=9.5V
IIN- vs input voltage
40
VIN+=20V VIN+=21V
45 40 35 IIN- (nA)
35 30 IIN- (nA)
T A = 25C
30 25 20 15 10
25 20 15 10 5
5 0 -40 -15 10 35 60 85
0
9
11
13
15
Input voltage (V)
17
19
21
Temperature (C)
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ZXCT1032
Typical characteristics (TA = 25C and VIN+ = 20V unless otherwise stated)
ICT-CHG vs temperature
0 -25 -50 -75 IC-CHG (uA) -100 -125 -150 -175 -200 -225 -250 -40 -15 10 35 Temperature (C) 60 85 -208 9 11 13 15 17 Input voltage (V) 19 21 -207 IC-CHG (uA)
VIN+ = 9.5 to 21V
ICT-CHG vs input voltage
-206.5
TA = 25C
-207.5
ICT-DIS vs temperature
5.0 4.5 4.0 3.5 IC-DIS (uA)
V IN+ = 9.5 to 21V
3.75
ICT-DIS vs input voltage
TA =25C
3.74
2.5 2.0 1.5 1.0 0.5 0.0 -40 -15 10 35 Temperature (C) 60 85
IC-DIS (uA)
3.0
3.73
3.72
3.71
3.70 9 11 13 15 17 19 21 Input voltage (V)
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ZXCT1032
Application information ZXCT1032 block diagram and description
R SENSE (8)
IN+
(6) +INZXCT1032 + + 50k 2.1V + 80mV Flag (4) Drive (5)
NC
ICT-CHG (3) ISET (2) CT CT GND (1) ICT-DIS 3.3 A 200 A
Load
Operation of the ZXCT1032
1 After power-up, the timing capacitor (CT) is charged up by a 200A current source. This causes the output amplifier's drive pin to fall in voltage, progressively turning on the PMOS transistor. The load current is monitored by the current monitor and the amplifier control loop controls the load current allowing it to increase gradually (soft-start mode) as the voltage on CT increases. During the soft-start phase the load current will start to build up while there is a large voltage across the pass MOSFET; this can lead to large power dissipation if large capacitive loads are driven and/or large CT is used.
ZXCT1032 Start up characteristic
3 1.2
VIN+ = 18V R SENSE = 0.2 2.5 C T = 220nF VISET = 2.1V Trip current = 1A
VCT VISET
1
Load current - A
Voltages - V
2
0.8
1.5
ILOAD
0.6
1
0.4
10*VSENSE
0.5 0.2
0 0 0.5 1 1.5 2 2.5
0
time - ms
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ZXCT1032
2 The output voltage also increases due to the load current powering up the load and charging any capacitance. After the initial soft start (load current stabilizing) the timing capacitor charges up to 4V and the device enters its normal mode of operation. The external MOSFET will be now fully enhanced minimizing any serial voltage drop.
ZXCT1032 Normal Operation
20 18
Timing capacitor voltage - V
VLOAD
1
16 14 12 10 8 6 4 2 0
0.8
Load Current - A
ILOAD
VIN+ = 18V RSENSE = 0.2 CT = 220nF VISET = 2.1V Trip current = 1A
0.6
0.4
VCT VISET 10*VSENSE
0 5 10 Time ms 15 20
0.2
0
The ZXCT1032 has now entered its over-current detector mode; it is effectively "transparent" to the load until the current monitor output exceeds the trip point. 3 Fuse operation is provided by the trip comparator whose threshold voltage is set by VISET (internally nominally 2.1V, although this threshold can easily be overdriven). As the load current increases, so does the monitor voltage. When the current monitor output voltage exceeds VISET, the trip comparator output goes high and sets the latch with the following results: a The output drive is disabled. b The open collector Flag output goes low to indicate a fault condition. c The 200 A current source is turned off and CT starts to discharge slowly via a 3.3 A current source.
ZXCT1032 Timing in over-current condition
2.5 2.5
VISET
2 VIN+ RSENSE = 18 V = 0.2 ? >1A = 220 nF 1.5 Load Current - A 2
Voltages - V
1.5
ILOAD
VCT
1
CT
VISET = 2.1 V Trip current = 1 A 1
0.5
0.5
ILOAD
0 0 50 Time (ms) 100 0 150
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ZXCT1032
4 When CT has discharged to "zero" (< 80mV) the latch is reset which re-enables the output drive and allows the device to re-enter soft-start mode. 5 In the event of an overload or short circuit, stages 3 and 4 repeat indefinitely until the fault is removed. In the case of a permanent fault damage to the PMOS transistor should not occur because it is only on for a short part of the overall cycle. 6 The current monitor has an intentional output offset of +150mV. If VISET is held at 0V, the output of the trip comparator will be permanently high and the output will be completely disabled.
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ZXCT1032
Package outline - SO8
DIM A A1 D H E L
Inches Min. 0.053 0.004 0.189 0.228 0.150 0.016 Max. 0.069 0.010 0.197 0.244 0.157 0.050
Millimeters Min. 1.35 0.10 4.80 5.80 3.80 0.40 Max. 1.75 0.25 5.00 6.20 4.00 1.27
DIM e b c h -
Inches Min. 0.013 0.008 0 0.010 Max. 0.020 0.010 8 0.020 0.050 BSC
Millimeters Min. 0.33 0.19 0 0.25 Max. 0.51 0.25 8 0.50 1.27 BSC
Note: Controlling dimensions are in inches. Approximate dimensions are provided in millimeters
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ZXCT1032
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) 2007 Published by Zetex Semiconductors plc
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