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2557
A2557xLB (SOIC)
OUT 1 K OUT 2 GROUND GROUND OUT 3 FAULT OUT 4 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 IN 1 IN 2 ENABLE GROUND GROUND V CC IN 3 IN 4
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 A. 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 temperature to reach approximately 165C 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.
Data Sheet 29317.16H
Dwg. PP-017-4
Note that the A2557xB (DIP) and the A2557xLB (SOIC) are electrically identical and share a common terminal number assignment.
ABSOLUTE MAXIMUM RATINGS
Output Voltage, VO .............................. 60 V Over-Current Protected Output Voltage, VO ..................................................... 32 V Output Current, IO ......................... 500 mA* FAULT Output Voltage, VFLT ............. 60 V Logic Supply Voltage, VCC ................. 7.0 V Input Voltage, VI or VOE ..................... 7.0 V Package Power Dissipation, PD ........................................... See Graph Operating Temperature Range, TA Suffix `S-' ...................... -20C to +85C Suffix `E-' ...................... -40C to +85C Suffix `K-' ................... -40C to +125C Junction Temperature, TJ ............................................... +150C* Storage Temperature Range, TS ................................. -55C to +150C
*Outputs are current limited at approximately 500 mA per driver and junction temperature limited if higher current is attempted.
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
2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
Selection Guide Part Number Pb-free Package Ambient Temperature (C) -20 to 85 -20 to 85 -20 to 85 -20 to 85 -20 to 85 -20 to 85 -40 to 85 -40 to 85 -40 to 85 -40 to 85 -40 to 85 -40 to 85 -40 to 125 -40 to 125 -40 to 125 -40 to 125 -40 to 125 -40 to 125
A2557SB A2557SB-T A2557SEB A2557SEB-T A2557SLB A2557SLB-T A2557EB A2557EB-T A2557EEB A2557EEB-T A2557ELB A2557ELB-T A2557KB A2557KB-T A2557KEB A2557KEB-T A2557KLB A2557KLB-T
- Yes - Yes - Yes - Yes - Yes - Yes - Yes - Yes - Yes
16-pin DIP,exposed tabs 16-pin DIP,exposed tabs 28-lead PLCC 28-lead PLCC 16-lead SOIC 16-lead SOIC 16-pin DIP,exposed tabs 16-pin DIP,exposed tabs 28-lead PLCC 28-lead PLCC 16-lead SOIC 16-lead SOIC 16-pin DIP,exposed tabs 16-pin DIP,exposed tabs 28-lead PLCC 28-lead PLCC 16-lead SOIC 16-lead SOIC
2
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
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
Dwg. FP-007-2
A2557xEB (PLCC)
NO CONNECTION ENABLE
ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS
OUT2
OUT1
5
IN 1
K
IN 2
NC GROUND 5 6 7 8 9 10 GROUND 11 NC VCC 25 24 23 22 21 20 19 GROUND GROUND
4
SUFFIX 'EB', R
JA
R JT = 6C/W = 36C/W
28
27
26
4
2
3
1
3
SUFFIX 'B', R
JA
= 43C/W
2
1
SUFFIX 'LB', R JA = 90C/W
15
12
13
14
16
17
18
NO CONNECTION
FAULT
OUT 4
OUT 3
IN 4
IN 3
SUPPLY
0
25
50
75 100 TEMPERATURE IN C
125
150
Dwg. PP-019-2
Dwg. GP-004-2B
3
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright (c) 1998, 2006 Allegro MicroSystems, Inc.
2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
ELECTRICAL CHARACTERISTICS over operating temperature range, VCC = 4.75 V to 5.25 V
Characteristic
Output Leakage Current* Output Sustaining Voltage Output Saturation Voltage Over-Current Limit Input Voltage Input Current Fault Output Leakage Current Fault Output Current Fault Output Saturation Voltage Clamp Diode Forward Voltage Clamp Diode Leakage Current Turn-On Delay
Symbol
ICEX VO(SUS) VO(SAT) IOM VIH VIL IIH IIL IFLT IFLT VFLT(SAT) VF IR tPHL
Test Conditions
VO = 60 V, VI = 0.8 V, VOE = 2.0 V VO = 60 V, VI = 2.0 V, VOE = 0.8 V IO = 100 mA, VI = VOE = 0.8 V, VCC = Open IO = 1 0 0 m A IO = 3 0 0 m A 5 ms PulseTest, VO = 5.0 V INn or ENABLE INn or ENABLE INn or ENABLE, VIH = 2.0 V INn or ENABLE, VIL = 0.8 V VFLT = 60 V VFLT = 5 V VFLT = 5 V, Driver Output Open, VI = 0.8 V, VOE = 2.0 V IFLT = 30 A IF = 5 0 0 m A IF = 7 5 0 m A VR = 60 V IO = 300 mA, 50% VI to 50% VO From Sleep, IO = 300 mA, 50% VI to 50% VO IO = 300 mA, 50% VOE to 50% VO
Min.
-- -- 40 -- -- -- 2.0 -- -- -- -- -- 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
Limits Typ. Max.
30 <1.0 -- 65 180 500 -- -- -- -- 4.0 <1.0 60 0.1 1.2 1.5 -- 0.6 3.0 1.3 2.0 1.4 0.075 12 18 24 30 165 100 100 -- 200 300 -- -- 0.8 10 -10 15 2.0 80 0.4 1.7 2.1 50 10 -- 10 10 10 0.1 20 30 40 50 --
Units
A A V mV mV mA V V A A A A A V V V A s s s s s mA mA mA mA mA C
Turn-Off Delay Total Supply Current
tPLH ICC
IO = 300 mA, 50% VI to 50% VO IO = 300 mA, 50% VOE to 50% VO All Outputs Off Any One Output On Two Outputs On Three Outputs On All Outputs On
Thermal Limit
TJ
Typical Data is at TA = +25C 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.
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2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
TYPICAL OPERATING CHARACTERISTICS
600
0.3 VCC = 5 V
OUTPUT CURRENT LIMIT IN MILLIAMPERES
OUTPUT SATURATION VOLTAGE IN VOLTS
TA = +25C VCC = 5 V 500
0.2
TA
=
12
C 5
5C
TA
0.1
=2
TA
=-
C 40
400
300
0
0
100
200
300
400
Dwg. GP-064
0
10
20
30
40
Dwg. GP-065
OUTPUT CURRENT IN MILLIAMPERES
OUTPUT VOLTAGE IN VOLTS
6 TA = +25C VCC = 5 V 4
TURN-OFF DELAY IN MICROSECONDS
3
TURN-ON DELAY IN MICROSECONDS
IN SWITCHING (FROM SLEEP)
TA = +25C VCC = 5 V 2
IN S
WIT
CH
2
ENA
ING
ENABLE SWITCHING
BLE
SW
ITC
HIN
G
1
IN SWITCHING (AWAKE)
0
0
100
200
300
400
Dwg. GP-066
0
OUTPUT CURRENT IN MILLIAMPERES
0
100
200
300
400
Dwg. GP-066-1
OUTPUT CURRENT IN MILLIAMPERES
5
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
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 Over-Current or Short to Supply Open Load or Short to Ground INN H L X All L H L ENABLE H H L X H H OUTN L H H H R L H FAULT H H H H L L L * if the power dissipation in the output device increases the local junction temperature above 165C (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 A. 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 commoncathode 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.
Thermal Fault H H 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 A 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 A output sinks are turned off. The FAULT output is a switched current sink of typically 60 A. 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
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115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
CIRCUIT DESCRIPTION AND APPLICATION (continued)
Fault diagnostics
NORMAL LAMP IN-RUSH CURRENT
NOT TO SCALE
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 k 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, opencircuit 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 A), 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.
LAMP CURRENT
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 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.
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115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
CIRCUIT DESCRIPTION AND APPLICATION (continued)
IN
NOT TO SCALE
WITH OUTPUT CAPACITOR
FAULT
OUTPUT CURRENT
(SHORTED LOAD)
FAULT
(OPEN LOAD)
Dwg. WP-035
SHORT CIRCUIT
NORMAL LOAD CURRENT LIMIT (12 V SUPPLY)
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 s (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 F) 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 -- unused outputs should not be turned on, or unused outputs should be pulled high to >2.5 V, and/or associated inputs tied low.
CURRENT LIMIT (24 V SUPPLY)
TIME
Dwg. WP-013-1
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') = 36C/W 16-pin PDIP (part number suffix `-B') = 43C/W 16-lead SOIC (part number suffix `-LB') = 90C/W RJA is measured on typical two-sided PCB. Additional information is available on the Allegro web site.
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2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
B Package, 16-pin DIP
with internally fused pins 4, 5, 12, and 13 and external thermal tabs
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
.775 19.69 .735 18.67 16
A B
.014 0.36 .008 0.20
.280 7.11 .240 6.10 A 1 2
.300 .7.62
.430 10.92 MAX
.195 4.95 .115 2.92 .015 0.38 MIN .100 .2.54 .022 .056 .014 .036 .010 [0.25] M C .150 3.81 .115 2.92
.210 5.33 MAX
SEATING PLANE
C
.005 0.13 MIN .070 1.78 .045 1.14 16X
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2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
EB Package, 28-pin PLCC
with internally fused pins 5 through 11 and 19 through 25
.495 12.57 .485 12.32 A .007 [0.18] H B A
.456 11.58 2X .450 11.43 .007 [0.18] H B A .002 [0.05] B
.456 11.58 2X .450 11.43 .007 [0.18] H B .002 [0.05] B
B 2 1 28
.020 0.51
A
.219 5.56 .191 4.85
.219 5.56 .191 4.85 .495 12.57 .485 12.32 .007 [0.18] H B A .020 0.51 MIN .120 3.05 .090 2.29 .032 0.81 .026 0.66 .007 [0.18] C B A 28X .004 [0.10] C 28X .021 0.53 .013 0.33 .007 [0.18] C B A .219 5.56 .191 4.85 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 Terminal #1 mark area .219 5.56 .191 4.85 .180 4.57 .165 4.19 H C
28X
SEATING PLANE
.050 1.27
10
115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000
2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
LB Package, 16-pin SOIC
with internally fused pins 4 and 5, and 12 and 13
10.63 .419 9.97 .393 0.25 [.010] M B M 10.50 .614 10.10 .598 A B 8 0 0.33 .013 0.20 .008
16
7.60 .299 7.40 .291 A 1.27 .050 0.40 .016
1
2 0.25 .010
16X 0.10 [.004] C 16X 0.51 .020 0.31 .012 0.25 [.010] M C A B 1.27 .050
SEATING PLANE 2.65 .104 2.35 .093 0.30 .012 0.10 .004
C
SEATING PLANE GAUGE 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
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2557 PROTECTED QUAD DRIVER WITH FAULT DETECTION & SLEEP MODE
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 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 responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use.
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