2557_06 ALLEGRO
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H61.71392 2557 PROTECTED QUAD LOW-SIDE DRIVER WITH FAULT DETECTION and SLEEP MODE The A2557xB, A2557xEB, and A2557xLB have been specifically designed to provide cost-effective solutions to relay-driving applications with up to 300 mA drive current per channel. They may also be used for driving incandescent lamps in applications where turn-on time is not a concern. Each of the four outputs will sink 300 mA in the on state. The outputs have a minimum breakdown voltage of 60 V and a sustaining voltage of 40 V. A low-power Sleep Mode is activated with either ENABLE low or all inputs low. In this mode, the supply current drops to below 100 µA. Over-current protection for each channel has been designed into these devices and is activated at a nominal 500 mA. It protects each output from short circuits with supply voltages up to 32 V. When an output experiences a short circuit, the output current is limited at the 500 mA current clamp. In addition, foldback circuitry decreases the current limit if an excessive voltage is present across the output and assists in keeping the device within its SOA (safe operating area). An exclusive-OR circuit compares the input and output state of each driver. If either a short or open load condition is detected, a single FAULT output is turned on (active low). Continuous or multiple overload conditions causing the channel tempera- ture to reach approximately 165°C will result in an additional linear decrease in the output current of the affected driver. If the fault condition is corrected, the output stage will return to its normal saturated condition. The packages offer fused leads for enhanced thermal dissipation. Package B is 16-pin power DIP with exposed tabs, EB is 28-lead power PLCCs, and LB are 16-lead power wide-body SOICs for surface-mount applications. The lead (Pb) free versions have 100% matte tin leadframe plating.
FEATURES
■ 300 mA Output Current per Channel ■ Independent Over-Current Protection &Thermal Limiting for Each Driver ■ Output Voltage to 60 V ■ Output SOA Protection ■ Fault-Detection Circuitry for Open or Shorted Load ■ Low Quiescent Current Sleep Mode ■ Integral Output Flyback/Clamp Diodes ■ TTL- and 5 V CMOS-Compatible Inputs A2557xLB (SOIC) Note that the A2557xB (DIP) and the A2557xLB (SOIC) are electrically identical and share a common terminal number assignment. ABSOLUTE MAXIMUM RATINGS Over-Current Protected Output Voltage, Package Power Dissipation, Operating Temperature Range, TA Junction Temperature, Storage Temperature Range, *Outputs are current limited at approximately 500 mA per driver and junction temperature limited if higher current is attempted. 3 14 8 9 ENABLE GROUND GROUND OUT 3 FAULT GROUND GROUND OUT 2 OUT 1 K OUT 4 V CC IN 4 Dwg. PP-017-4 IN 1 IN2 IN 3
& SLEEP MODE
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-50002 Selection Guide Part Number Pb-free Package Ambient Temperature (°C) A2557SB – 16-pin DIP,exposed tabs –20 to 85 A2557SB-T Yes 16-pin DIP,exposed tabs –20 to 85 A2557SEB – 28-lead PLCC –20 to 85 A2557SEB-T Yes 28-lead PLCC –20 to 85 A2557SLB – 16-lead SOIC –20 to 85 A2557SLB-T Yes 16-lead SOIC –20 to 85 A2557EB – 16-pin DIP,exposed tabs –40 to 85 A2557EB-T Yes 16-pin DIP,exposed tabs –40 to 85 A2557EEB – 28-lead PLCC –40 to 85 A2557EEB-T Yes 28-lead PLCC –40 to 85 A2557ELB – 16-lead SOIC –40 to 85 A2557ELB-T Yes 16-lead SOIC –40 to 85 A2557KB – 16-pin DIP,exposed tabs –40 to 125 A2557KB-T Yes 16-pin DIP,exposed tabs –40 to 125 A2557KEB – 28-lead PLCC –40 to 125 A2557KEB-T Yes 28-lead PLCC –40 to 125 A2557KLB – 16-lead SOIC –40 to 125 A2557KLB-T Yes 16-lead SOIC –40 to 125
& SLEEP MODE Worcester, Massachusetts 01615-0036 (508) 853-50003 Copyright © 1998, 2006 Allegro MicroSystems, Inc. FUNCTIONAL BLOCK DIAGRAM <<1 Ω OUT Dwg. FP-007-2 N ENABLE IN N FAULT COMMON CONTROL ONE OF FOUR DRIVERS CURRENT LIMIT THERMAL LIMIT SLEEP CONTROL 30 µA 60 µA 2.5 V– K V CC A2557xEB (PLCC) 50 75 100 125 150 ALLOWABLE PACKAGE POWER DISSIPATION IN WATTSTEMPERATURE IN °°°°C R = 6°C/WθJT Dwg. GP-004-2B SUFFIX 'EB', R = 36°C/WθJA SUFFIX 'B', R = 43°C/WθJA SUFFIX 'LB', R = 90°C/WθJA 412 18 26 GROUND GROUND GROUND GROUND Dwg. PP-019-2 NO CONNECTION ENABLESUPPLY NC NC CCV OUT1 OUT2OUT3 OUT 4 IN4 IN3 IN2 IN1 NO CONNECTION KFAULT 255
& SLEEP MODE www.allegromicro.com 4 Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units Output Leakage Current* ICEX VO = 60 V, VI = 0.8 V, VOE = 2.0 V — 30 100 µA VO = 60 V, VI = 2.0 V, VOE = 0.8 V — <1.0 100 µA Output Sustaining Voltage VO(SUS) IO = 100 mA, VI = VOE = 0.8 V, VCC = Open 40 — — V Output Saturation Voltage VO(SAT) IO Vm00256—Am 001 = IO Vm003081—Am 003 = Over-Current Limit IOM 5 ms PulseTest, VO Am—005—V 0.5 = VegatloV tupnI IH INn V——0.2ELBANE ro VIL INn V8.0——ELBANE ro ItnerruC tupnI IH INn or ENABLE, VIH 01——V 0.2 = µA IIL INn or ENABLE, VIL 01-——V 8.0 = µA Fault Output Leakage Current IFLT VFLT 510.4—V 06 = µA VFLT 0.20.1<—V 5 = µA Fault Output Current IFLT VFLT = 5 V, Driver Output Open , VI = 0.8 V, VOE 080604V 0.2 = µA Fault Output Saturation Voltage VFLT(SAT) IFLT = 30 µ V4.01.0—A Clamp Diode Forward Voltage VF IF V7.12.1—Am 005 = IF V1.25.1—Am 057 = Clamp Diode Leakage Current IR VR 05——V 06 = µA tyaleD nO-nruT PHL IO = 300 mA, 50% VI to 50% VO — 0.6 10 µs From Sleep, IO = 300 mA, 50% VI to 50% VO — 3.0 — µs IO = 300 mA, 50% VOE to 50% VO — 1.3 10 µs tyaleD ffO-nruT PLH IO = 300 mA, 50% VI to 50% VO — 2.0 10 µs IO = 300 mA, 50% VOE to 50% VO — 1.4 10 µs Total Supply Current ICC Am1.0570.0—ffO stuptuO llA Am0221—nO tuptuO enO ynA Am0381—nO stuptuO owT Am0442—nO stuptuO eerhT Am0503—nO stuptuO llA TtimiL lamrehT J — 165 — °C ELECTRICAL CHARACTERISTICS over operating temperature range, VCC = 4.75 V to 5.25 V Typical Data is at TA = +25°C and VCC = 5 V and is for design information only. Negative current is defined as coming out of (sourcing) the specified terminal. As used here, -100 is defined as greater than +10 (absolute magnitude convention) and the minimum is implicitly zero. * Measurement includes output fault-sensing pull-down current.
& SLEEP MODE Worcester, Massachusetts 01615-0036 (508) 853-50005 TYPICAL OPERATING CHARACTERISTICS 100 Dwg. GP-064 200 400300 OUTPUT CURRENT IN MILLIAMPERES 0.3 0.2 OUTPUT SATURATION VOLTAGE IN VOLTS 0.1 VCC = 5 V TA = 125 TA = 25 TA = -40 Dwg. GP-065 20 4030 OUTPUT VOLTAGE IN VOLTS 600 500 400 300 OUTPUT CURRENT LIMIT IN MILLIAMPERES TA = +25°C VCC = 5 V 100 Dwg. GP-066-1 200 400300 OUTPUT CURRENT IN MILLIAMPERES TURN-ON DELAY IN MICROSECONDS TA = +25°C VCC = 5 V ENABLE SWITCHING IN SWITCHING (FROM SLEEP) IN SWITCHING (AWAKE) 100 Dwg. GP-066 200 400300 OUTPUT CURRENT IN MILLIAMPERES TURN-OFF DELAY IN MICROSECONDS TA = +25°C VCC = 5 V ENABLE SWITCHING IN SWITCHING
& SLEEP MODE Worcester, Massachusetts 01615-0036 (508) 853-50006 The A2557 low-current quad power drivers provide protected output driver functions, combined with a fault diagnostic scheme, plus an automatic low-current Sleep-Mode function. These devices monitor their outputs for fault (open or shorted) conditions. For each channel the input and output levels are compared. If these are different from the expected levels then a fault condition is flagged by pulling the common FAULT output low. Status IN N ENABLE OUT N FAULT Normal Load HH L H LH H H Sleep Mode XL H H All L X H H Over-Current or Short to Supply HH R L Open Load or Short to Ground LH L L Thermal Fault H H H L R = Linear drive, current limited. The FAULT output is operational only if ENABLE is high. The output state is detected by monitoring the OUT n terminal using a comparator whose threshold is typically 2.5 V. In order to detect open-circuit outputs, a 30 µA current sink pulls the output below the comparator threshold. To ensure correct fault operation, a minimum load of approximately 1 mA is required. The fault function is disabled when in ‘sleep’ mode, i.e., FAULT goes high and the 30 µA output sinks are turned off. The FAULT output is a switched current sink of typically 60 µA. Each channel consists of a TTL/CMOS-compatible logic input gated with a common ENABLE input. A logic high at the input will provide drive to turn on the output npn switch. Each output has a current-limit circuit that limits the output current by detecting the voltage drop across a low-value internal resistor in the emitter of the output switch. If this drop reaches a threshold, then the base drive to the output switch is reduced to maintain constant current in the output. To keep the device within its safe operating area (SOA) this output current limit is further reduced CIRCUIT DESCRIPTION AND APPLICATION if the power dissipation in the output device increases the local junction temperature above 165°C (nominal), so as to limit the power dissipation (and hence the local junction tempera- ture). As each channel has its own thermal limit circuitry this provides some independence between the output channels, i.e., one channel can be operating in thermally reduced current limit, while the others can provide full drive capability. as a function of the output voltage. Full current limit of 500 mA (nominal) is available up to approximately V O = 8 V; above this the limit is reduced linearly to about 350 mA at V O = 32 V. This helps to improve SOA by immediately reducing the peak power pulse into a shorted load at high V O. A logic low at the ENABLE input causes all outputs to be switched off regardless of the state of the IN terminals. In addition, the device is put into a low quiescent current ‘sleep’ mode, reducing I CC below 100 µA. If ENABLE is taken high and any of the inputs go high, the circuit will ‘auto-wake-up’. However, if the device is enabled, but all inputs stay low, then the circuit remains in ‘sleep’ mode. All outputs have internal flyback diodes, with a common- cathode connection at the K terminal. Incandescent lamp driver High incandescent lamp turn-on (in-rush currents) can contribute to poor lamp reliability and destroy semiconductor lamp drivers. When an incandescent lamp is initially turned on, the cold filament is at minimum resistance and would normally allow a 10x to 12x in-rush current. Warming (parallel) or current-limiting (series) resistors protect both driver and lamp but use significant power either when the lamp is off or when the lamp is on, respectively. Lamps with steady-state current ratings up to 300 mA can be driven without the need for warming or current-limiting resis- tors, if lamp turn-on time is not a concern (10s of ms). With these drivers, during turn-on, the high in-rush current is sensed by the internal sense resistor, drive current to the output stage is reduced, and the output operates in a linear mode with the load current limited to approximately 500 mA. During lamp warmup, the filament resistance increases to its maximum value, the output driver goes into saturation and applies maxi- mum rated voltage to the lamp.
& SLEEP MODE Worcester, Massachusetts 01615-0036 (508) 853-50007 CIRCUIT DESCRIPTION AND APPLICATION (continued) Fault diagnostics A pull-up resistor or current source is required on the FAULT output. This can be connected to whatever supply level the following circuitry requires (within the specification constraints). For a 5 V supply (i.e., Vcc) 150 kΩ or greater should be used. As the fault diagnostic function is to indicate when the output state is different from the input state for any channel, the FAULT output waveform will obviously produce a pulse waveform following the combined duty-cycle of all channels showing a fault condition. There are therefore two basic approaches to using the function in an application:
- As an interrupt in a controller-based system. If the system has a microcontroller then a FAULT low causes an interrupt, which then initiates a diagnostic sequence to find the culprit channel. This sequence usually consists of cycling through each channel one at a time, while monitoring the FAULT output. It is then easy to determine which channel has the faulty output and how it is failing (i.e., short to supply, open- circuit or short to ground). The system may then take whatever action is required, but could continue with operation of the remaining ‘good’ channels while disabling signals to the faulty channel.
- As a simple ‘common’ fault indication. If there is no controller in the system then the FAULT output can be set to give an indication (via a lamp or LED, etc.) of a fault condition which might be anywhere on the four channels. Because the FAULT output is dependent on the states of the input and output (four possibilities) but will only indicate on two of them, the duty cycle at the FAULT output will reflect the duty cycle at the faulty channel’s input (or its inverse, depending upon fault type). In typical applications (50% duty cycles) a simple solution is to make the pull-up current on the FAULT output much less than the pull-down current (60 µA), and add a capacitor to give a time constant longer than the period of operation. For typical values, the device will produce a continuous dc output level. Component values will need to be adjusted to cope with different conditions. Inductive load driver Bifilar (unipolar) stepper motors (and other inductive loads) can be driven directly. The internal diodes prevent damage to the output transistors by suppressing the high-voltage spikes that occur when turning off an inductive load. For rapid current decay (fast turn-off speeds), the use of Zener diodes will raise the flyback voltage and improve performance. However, the peak voltage must not exceed the specified minimum sustaining voltage (VSUPPLY + VZ + VF < VO(SUS)). Over-current conditions In the event of a shorted load, or stalled motor, the load current will attempt to increase. As described above, the drive current to the affected output stage is linearly reduced, causing the output to go linear (limiting the load current to about 500 mA). As the junction temperature of the output stage increases, the thermal-shutdown circuit will shut off the affected output. If the fault condition is corrected, the output driver will return to its normal saturated condition. NORMAL LAMP IN-RUSH CURRENT TIME THERMAL GRADIENT SENSING CURRENT LIMIT Dwg. WP-008 NOT TO SCALE ITRIP LAMP CURRENT
& SLEEP MODE www.allegromicro.com 8 CIRCUIT DESCRIPTION AND APPLICATION (continued) NORMAL LOAD TIME Dwg. WP-013-1 NOT TO SCALE OUTPUT CURRENT CURRENT LIMIT (12 V SUPPLY) SHORT CIRCUIT CURRENT LIMIT (24 V SUPPLY) IN FAULT (SHORTED LOAD) FAULT (OPEN LOAD) WITH OUTPUT CAPACITOR Dwg. WP-035 Thermal considerations Device power dissipation can be calculated as: PD = (VO1 x IO1 x duty cycle1) + … + (VO4 x IO4 x duty cycle4) + (VCC x ICC) Note - ICC is also modulated by the duty cycle, but this is a reasonable approximation for most purposes. This can then be compared against the permitted package power dissipation, using: Permitted PD = (150 – TA)/RθJA where RθJA is given as: 28-lead PLCC (part number suffix ‘–EB’) = 36°C/W 16-pin PDIP (part number suffix ‘–B’) = 43°C/W 16-lead SOIC (part number suffix ‘–LB’) = 90°C/W RθJA is measured on typical two-sided PCB. Additional Under some conditions it is possible to get spurious glitches on the FAULT output at load turn-on and turn-off transitions:
- Light load turn-off. Under light loading conditions the turn-off delay (see characteristics above) of the output stage increases and may result in a spurious fault output of a few µs (the duration being proportional to the turn-off delay). As it is difficult to define this over all operating conditions, if a particular application would be sensitive to this type of glitch, then it is generally recommended to include a small (about 0.01 µF) smoothing/storage capacitor at the FAULT output.
- Incandescent lamp turn-on. As described above, driving an incandescent filament results in the driver operating in current limit for a period after turn-on. During this period a “fault” condition will be indicated (over current). As discussed above this period can be 10s of ms. To avoid this indication, the capacitor on the FAULT output would need to be increased to provide an appropriate time constant. Alternatively, in a microcontroller-based system, the code could be written to ignore the FAULT condition for an appropriate period after lamp turn on. Correct FAULT operation cannot be guaranteed with an unconnected output — u nused outputs should not be turned on, or unused outputs should be pulled high to >2.5 V, and/or associated inputs tied low. information is available on the Allegro web site.
& SLEEP MODE www.allegromicro.com 9 B Package, 16-pin DIP with internally fused pins 4, 5, 12, and 13 and external thermal tabs .070 .045 1.78 1.14 .150 .115 3.81 2.92 .195 .115 4.95 2.92 .014 .008 0.36 0.20 .430 MAX 10.92 .015 MIN 0.38 .005 MIN 0.13 .280 .240 7.11 6.10 .775 .735 19.69 18.67 A B CSEATING PLANE .022 .014 .056 .036 16X .010 [0.25] M C .100 .2.54 .300 .7.62 .210 MAX 5.33 A Preliminary dimensions, for reference only Dimensions in inches Metric dimensions (mm) in brackets, for reference only (reference JEDEC MS-001 BB) Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Terminal #1 mark area
& SLEEP MODE Worcester, Massachusetts 01615-0036 (508) 853-500010 with internally fused pins 5 through 11 and 19 through 25 21 2 8 A Terminal #1 mark area Preliminary dimensions, for reference only (reference JEDEC MS-018 AB) Dimensions in inches Millimeters (mm) in brackets, for reference only Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A .120 .090 3.05 2.29 .180 .165 4.57 4.19 11.58 11.43 .456 .450 5.56 4.85 .219 .191 5.56 4.85 .219 .191 5.56 4.85 .219 .191 5.56 4.85 .219 .191 .020 MIN 0.51 C H SEATING PLANE .032 .026 0.81 0.66 28X C.004 [0.10] 28X .007 [0.18] H B A A 12.57 12.32 .495 .485 .007 [0.18] H B A 12.57 12.32 .495 .485 .007 [0.18] H B B.002 [0.05] .050 1.27 .020 0.51 A B 11.58 11.43 .456 .450 .007 [0.18] H B B.002 [0.05] A.007 [0.18] C B .021 .013 0.53 0.33 28X A.007 [0.18] C B
& SLEEP MODE www.allegromicro.com 11 with internally fused pins 4 and 5, and 12 and 13 0.30 0.10 .012 .004 2.65 2.35 .104 .093 7.60 7.40 .299 .291 0.33 0.20 .013 .008 1.27 0.40 .050 .016 10.50 10.10 .614 .598 CSEATING PLANE A B C0.10 [.004] 16X 0.25 .010 0.51 0.31 .020 .01216X 0.25 [.010] M C A B 10.63 9.97 .419 .393 0.25 [.010] M B M 1.27 .050 GAUGE PLANE SEATING PLANE Preliminary dimensions, for reference only Dimensions in millimeters U.S. Customary dimensions (in.) in brackets, for reference only (reference JEDEC MS-013 AA) Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Terminal #1 mark area A
& SLEEP MODE www.allegromicro.com 12 The products described here are manufactured under one or more Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsi- bility for its use; nor for any infringement of patents or other rights of third parties which may result from its use.