A2557 Protected Quad Driver with Fault Detection and Sleep Mode Features and Benefits Description ▪ 300 mA output current per channel ▪ Independent overcurrent protection and 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 The A2557 has been specifically designed to provide costeffective 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. Packages: Package B, 16-pin DIP with exposed tabs Not to scale Package EB, 28-pin PLCC with internally fused pins Overcurrent 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). Continued on the next page… Package LB, 16-pin SOIC with internally fused pins Functional Block Diagram FAULT ENABLE SLEEP CONTROL 60 A K COMMON CONTROL ONE OF FOUR DRIVERS V CC – 2.5 V + OUTN IN N THERMAL LIMIT CURRENT LIMIT 30 A <<1 29317.16L Protected Quad Driver with Fault Detection and Sleep Mode A2557 Description (continued) Continuous or multiple overload conditions causing the channel temperature 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 a 16-pin power DIP with exposed tabs, EB is a 28lead power PLCC, and LB is a 16-lead power wide-body SOIC for surface-mount applications. The lead (Pb) free versions have 100% matte tin leadframe plating. Selection Guide Part Number A2557EB-T* Pb-free Yes Package Packing 16-pin DIP, exposed tabs 25 pieces per tube A2557EEBTR-T* Yes 28-lead PLCC 800 pieces per reel A2557ELBTR-T* Yes 16-lead SOIC 1000 pieces per reel – 16-pin DIP, exposed tabs 25 pieces per tube A2557KB-T* Yes 16-pin DIP, exposed tabs 25 pieces per tube A2557KEBTR-T* Yes 28-lead PLCC 800 pieces per reel A2557KLBTR* – 16-lead SOIC 1000 pieces per reel A2557KLBTR-T Yes 16-lead SOIC 1000 pieces per reel A2557SB-T* Yes 16-pin DIP, exposed tabs 25 pieces per tube A2557SEBTR-T* Yes 28-lead PLCC 800 pieces per reel A2557SLBTR-T* Yes 16-lead SOIC 1000 pieces per reel A2557KB* Ambient Temperature (°C) –40 to 85 –40 to 125 –20 to 85 *Variant is in production but has been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of the variant is currently restricted to existing customer applications. The variant should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Status change: May 4, 2009. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 Protected Quad Driver with Fault Detection and Sleep Mode A2557 Absolute Maximum Ratings Characteristic Symbol Logic Supply Voltage Input Voltage Output Voltage Overcurrent Protected Output Voltage Output Current 7.0 V 7.0 V VO 60 V VO(OCP) 32 V 500 mA 60 V – – Outputs current-limited to approximately 500 mA per driver, and TJ limited if higher current is attempted VFLT PD Operating Ambient Temperature TA Maximum Junction Temperature TJ(max) Tstg ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS Units VCC Package Power Dissipation Storage Temperature Rating VI or VOE IO FAULT Output Voltage Notes See graph Range E –40 to 85 ºC Range K –40 to 125 ºC Range S –20 to 85 ºC 150 ºC –55 to 150 ºC 5 R QJT = 6oC/W 4 SUFFIX 'EB', R QJA = 36oC/W 3 SUFFIX 'B', R QJA = 43oC/W 2 1 SUFFIX 'LB', R QJA = 90oC/W 0 25 50 75 100 TEMPERATURE IN o C 125 150 Dwg. GP-004-2B Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 Protected Quad Driver with Fault Detection and Sleep Mode A2557 Pin-out Diagrams IN 1 IN 2 ENABLE 28 27 26 OUT1 2 1 K 3 NO CONNECTION OUT2 4 EB (PLCC) Package NC 25 6 24 7 23 8 22 9 21 10 20 11 19 GROUND GROUND VCC 13 14 15 16 17 18 FAULT OUT 4 NO CONNECTION IN 4 IN 3 SUPPLY NC 12 GROUND 5 OUT 3 GROUND Dwg. PP-019-2 B (DIP) and LB (SOIC) Packages OUT1 1 16 IN 1 K 2 15 IN2 OUT2 3 14 ENABLE GROUND 4 13 GROUND GROUND 5 12 GROUND OUT3 6 11 V CC FAULT 7 10 IN 3 8 9 IN 4 OUT4 Note that the A2557xB (DIP) and the A2557xLB (SOIC) are electrically identical and share a common terminal number assignment. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com Copyright © 1998, 2002 Allegro MicroSystems, Inc. 4 Protected Quad Driver with Fault Detection and Sleep Mode A2557 ELECTRICAL CHARACTERISTICS over operating temperature range, VCC = 4.75 V to 5.25 V Characteristic Output Leakage Current* Symbol ICEX Test Conditions Min. Limits Typ. Max. Units 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 = 100 mA — 65 200 mV IO = 300 mA — 180 300 mV 5 ms PulseTest, VO = 5.0 V — 500 — mA Over-Current Limit IOM Input Voltage VIH INn or ENABLE 2.0 — — V VIL INn or ENABLE — — 0.8 V IIH INn or ENABLE, VIH = 2.0 V — — 10 μA IIL INn or ENABLE, VIL = 0.8 V — — -10 μA VFLT = 60 V — 4.0 15 μA VFLT = 5 V — <1.0 2.0 μA VFLT = 5 V, Driver Output Open, VI = 0.8 V, VOE = 2.0 V 40 60 80 μA VFLT(SAT) IFLT = 30 μA — 0.1 0.4 V Clamp Diode Forward Voltage VF IF = 500 mA — 1.2 1.7 V IF = 750 mA — 1.5 2.1 V Clamp Diode Leakage Current IR VR = 60 V — — 50 μA 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 Input Current Fault Output Leakage Current Fault Output Current Fault Output Saturation Voltage Turn-On Delay Turn-Off Delay Total Supply Current Thermal Limit IFLT IFLT tPHL tPLH ICC TJ IO = 300 mA, 50% VOE to 50% VO — 1.3 10 μs IO = 300 mA, 50% VI to 50% VO — 2.0 10 μs IO = 300 mA, 50% VOE to 50% VO — 1.4 10 μs All Outputs Off — 0.075 0.1 mA Any One Output On — 12 20 mA Two Outputs On — 18 30 mA Three Outputs On — 24 40 mA All Outputs On — 30 50 mA — 165 — °C 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. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 Protected Quad Driver with Fault Detection and Sleep Mode A2557 TYPICAL OPERATING CHARACTERISTICS 0.3 VCC = 5 V OUTPUT CURRENT LIMIT IN MILLIAMPERES OUTPUT SATURATION VOLTAGE IN VOLTS 600 oC 5 0.2 T A = 12 5 oC TA =2 oC 40 =- TA 0.1 0 0 100 200 300 T A = +25oC VCC = 5 V 500 400 300 400 0 OUTPUT CURRENT IN MILLIAMPERES 10 20 40 30 OUTPUT VOLTAGE IN VOLTS Dwg. GP-064 Dwg. GP-065 T A = +25oC VCC = 5 V 4 IN S WIT ENA 2 0 BLE 0 100 200 CH SW ING ITC HIN G 300 IN SWITCHING (FROM SLEEP) 3 TURN-ON DELAY IN MICROSECONDS TURN-OFF DELAY IN MICROSECONDS 6 400 OUTPUT CURRENT IN MILLIAMPERES Dwg. GP-066 T A = +25oC VCC = 5 V 2 ENABLE SWITCHING 1 IN SWITCHING (AWAKE) 0 0 100 200 400 300 OUTPUT CURRENT IN MILLIAMPERES Dwg. GP-066-1 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 Protected Quad Driver with Fault Detection and Sleep Mode A2557 CIRCUIT DESCRIPTION AND APPLICATION 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 Normal Load Sleep Mode INN ENABLE OUTN FAULT H H L H L H H H X L H H All L X H H Over-Current or Short to Supply H H R L Open Load or Short to Ground L H 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 OUTn 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: • 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 temperature). 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 VO = 8 V; above this the limit is reduced linearly to about 350 mA at VO = 32 V. This helps to improve SOA by immediately reducing the peak power pulse into a shorted load at high VO. 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 ICC 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 resistors, 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 maximum rated voltage to the lamp. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 Protected Quad Driver with Fault Detection and Sleep Mode A2557 CIRCUIT DESCRIPTION AND APPLICATION (continued) NORMAL LAMP IN-RUSH CURRENT 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: LAMP CURRENT NOT TO SCALE THERMAL GRADIENT SENSING CURRENT LIMIT ITRIP 0 TIME Dwg. WP-008 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 thermalshutdown circuit will shut off the affected output. If the fault condition is corrected, the output driver will return to its normal saturated condition. • 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. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 Protected Quad Driver with Fault Detection and Sleep Mode A2557 CIRCUIT DESCRIPTION AND APPLICATION (continued) OUTPUT CURRENT NOT TO SCALE IN FAULT (SHORTED LOAD) SHORT CIRCUIT NORMAL LOAD WITH OUTPUT CAPACITOR CURRENT LIMIT (12 V SUPPLY) FAULT (OPEN LOAD) CURRENT LIMIT (24 V SUPPLY) Dwg. WP-035 TIME Dwg. WP-013-1 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 turnoff 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 microcontrollerbased system, the code could be written to ignore the FAULT condition for an appropriate period after lamp turn on. 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)/RJA where RJA 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 RJA is measured on typical two-sided PCB with minimal copper ground area. Additional information is available on the Allegro website. Correct FAULT operation cannot be guaranteed with an unconnected output — unused outputs should not be turned on, or unused outputs should be pulled high to >2.5 V, and/or associated inputs tied low. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 Protected Quad Driver with Fault Detection and Sleep Mode A2557 B Package, 16-pin DIP with internally fused pins 4, 5, 12, and 13 and external thermal tabs 19.05±0.25 16 +0.10 0.38 –0.05 +0.76 6.35 –0.25 +0.38 10.92 –0.25 7.62 A 1 2 5.33 MAX +0.51 3.30 –0.38 1.27 MIN +0.25 1.52 –0.38 2.54 For Reference Only (reference JEDEC MS-001 BB) Dimensions in millimeters 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 0.46 ±0.12 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 Protected Quad Driver with Fault Detection and Sleep Mode A2557 EB Package, 28-pin PLCC with internally fused pins 5 through 11 and 19 through 25 12.45±0.13 11.51±0.08 2 1 0.51 28 A 12.45±0.13 5.21±0.36 11.51±0.08 5.21±0.36 0.74 ±0.08 4.57 MAX 28X SEATING PLANE 0.10 C C 0.43 ±0.10 1.27 5.21±0.36 5.21±0.36 For Reference Only (reference JEDEC MS-018 AB) Dimensions in millimeters 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 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 Protected Quad Driver with Fault Detection and Sleep Mode A2557 LB Package, 16-pin SOIC with internally fused pins 4 and 5, and 12 and 13 10.30±0.20 4° ±4 16 1.27 0.65 16 +0.07 0.27 –0.06 10.30±0.33 7.50±0.10 9.50 A +0.44 0.84 –0.43 2.25 1 2 1 0.25 16X SEATING PLANE 0.10 C 0.41 ±0.10 1.27 C 2 B PCB Layout Reference View SEATING PLANE GAUGE PLANE 2.65 MAX 0.20 ±0.10 For Reference Only Pins 4 and 5, and 12 and 13 internally fused Dimensions in millimeters (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 B Reference pad layout (reference IPC SOIC127P1030X265-16M) All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances Copyright ©1998-2009, Allegro MicroSystems, Inc. The products described here are manufactured under one or more U.S. patents or U.S. patents pending. 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’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. For the latest version of this document, visit our website: www.allegromicro.com Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 12