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L295
DUAL SWITCH-MODE SOLENOID DRIVER
PRELIMINARY DATA
HIGH CURRENT CAPABILITY (up to 2.5A per channel) HIGH VOLTAGE OPERATION (up to 46V for power stage) HIGH EFFICIENCY SWITCHMODE OPERATION REGULATED OUTPUT CURRENT (adjustable) FEW EXTERNAL COMPONENTS SEPARATE LOGIC SUPPLY THERMAL PROTECTION DESCRIPTION The L295 is a monolithic integrated circuit in a 15 lead Multiwatt (R) package; it incorporates all the functions for direct interfacing between digital circuitry and inductive loads. The L295 is designed to accept standard microprocessor logic levels at the inputs and can drive 2 solenoids. The output current is completely controlled by means of a switchABSOLUTE MAXIMUM RATINGS
Symbol Vs Vss VEN, Vi Vref Io Parameter Supply voltage Logic supply voltage Enable and input voltage Reference voltage Peak output current (each channel) - non repetitive (t = 100 sec) - repetitive (80% on - 20% off; Ton = 10 ms) - DC operation Ptot Tstg, Tj Total power dissipation (at Tcase = 75 C Storage and junction temperature
Multiwatt 15
ORDER CODE : L295
ing technique allowing very efficient operation. Furthermore, it includes an enable input and dual supplies (for interfacing with peripherals running at a higher voltage than the logic). The L295 is particularly suitable for applications such as hammer driving in matrix printers, step motor driving and electromagnet controllers.
Value 50 12 7 7 3 2.5 2 25 - 40 to 150 Unit V V V V A A A W C
APPLICATION CIRCUIT
March 1993
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CONNECTION DIAGRAM (top view)
BLOCK DIAGRAM
THERMAL DATA
Symbol Rth-j-case Rth-j-amb Parameter Thermal resistance junction-case Thermal resistance junction-ambient max max Value 3 35 Unit C/W C/W
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ELECTRICAL CHARACTERISTICS (Refer to the application circuit, Vss = 5V, Vs = 36V; Tj = 25C; L = Low; H = High; unless otherwise specified)
Symbol Vs Vss Id Iss Vi1,,Vi2 Parameter Supply Voltage Logic Supply Voltage Quiescent drain current (from VSS) Quiescent drain current (from VS) Input Voltage VS = 46V; Vi1 = Vi2 = VEN = L VSS = 10 V Low High VEN Enable Input Voltage Low High Ii1, Ii2 Input Current Vi1 = Vi2 = L Vi1 = Vi2 = H IEN Enable Input Current VEN = L VEN = H Vref1, Vref2 Iref1, Iref2m Fosc Ip Vref Vdrop Vsens1 Vsens2 Total output voltage drop (each channel) (*) External sensing resistors voltage drop Io = 2 A 2.8 3.6 2 V V Input Reference Voltage Input Reference Voltage Oscillation Frequency Transconductance (each ch.) C = 3.9 nF; Vref = 1V R = 9.1 K 1.9 25 2 2.1 0.2 -0.3 2.2 -0.3 2.2 Test conditions Min. 12 4.75 Typ. Max. 46 10 4 46 0.8 7 0.8 7 -100 10 -100 10 2 -5 V A KHz A/V A A V Unit V V mA mA
V
(*) Vdrop = VCEsat Q1 + VCEsat Q2.
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APPLICATION CIRCUIT
D2, D4 = 2A High speed diodes D1, D3 = 1A High speed diodes R1 = R2 = 2 L1 = L2 = 5 mH
)
trr 200 ns
FUNCTIONAL DESCRIPTION The L295 incorporates two indipendent driver channals with separate inputs and outputs, each capable of driving an inductive load (see block diagram). The device is controlled by three micriprocessor compatible digital inputs and two analog inputs. These inputs are: chip enable (digital input, active low), enables both channels when in the low state. Vin1, Vin2 channel inputs (digital inputs, active high), enable each channel independently. A channel is actived when both EN and the appropriate channel input are active. Vref1, Vref2 referce voltages (analog inputs), used to program the peak load currents. Peak load current is proportional to Vref . Since the two channels are identical, only channel one will be described. The following description applies also the channel two, replacing FF2 for FF1, Vref for Vref1 etc. When the channel is avtivated by low level on the EN input and a high level on the channel input, Vin2, the output transistors Q1 and Q2 switch on and EN current flows in the load according to the exponential law: I= where: V R1 (1 - e - R1 t L1 )
R1 and R2 are the resistance and inductance of the load and V is the voltage available on the load (Vs - Vdrop Vsense).
The current increases until the voltage on the external sensing resistor, RS1, reaches the reference voltage, Vref1. This peak current, Ip1, is given by: Ip1 = Vref1 RS1
At this point the comparator output, Vomp1, sete the RS flip-flop, FF1, that turns off the output transistor, Q1. The load current flowing through D2, Q2, RS1, decreases according to the law: I=( VA R1 + Ip1 ) e - R1 t L1 - VA R1
where VA = VCEsat Q2 + Vsense + VD2
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If the oscillator pin (9) is connected to ground the load current falls to zero as shown in fig. 1. At this time t2 the channel 1 is disabled, by taking the inputs Vin1 low and/or EN high, and the output transistor Q2 is turned off. The load current flows through D2 and D1 according to the law: I=( VB R1 + IT2 ) e - R1 t L1 - VB R1
where VB = VS + VD1 + VD2 IT2 = current value at the time t2. Fig. 2 in shows the current waveform obtained with an RC network connected between pin 9 and ground. From to t1 the current increases as in fig. 1. A difference exists at the time t2 because the current starts to increase again. At this time a pulse is produced by the oscillator circuit that resets the flip.flop, FF1, and switches on the outout transistor, Q1. The current increases until the drop on the sensing resistor RS1 is equal to Vref1 (t3) and the cycle repeats. SIGNAL WAVEFORMS Figure 1. Load current waveform with pin 9 connected to GND.
The switching frequency depends on the value R and C, as shown in fig. 4 and must be chosen in the range 10 to 30 KHz. It is possible with external hardware to change the reference voltage Vref in order to obtain a high peak current Ip and a lower holding current Ih (see fig. 3). The L295 is provided with a thermal protection that switches off all the output transistors when the junction temperature exceeds 150C. The presence of a hysteresis circuit makes the IC work again aftera fall of the junction temperature of about 20C. The analog input pins (Vref1 , Vref2) can be left open or connected to Vss; in this case the circuit works with an internal reference voltage of about 2.5V and the peak current in the load is fixed only by the value of Rs: Ip = 2.5 RS
Figure 2. Load current waveform with external R-C network connected between pin 9 and ground.
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SIGNAL WAVEFORMS (continued) Figure 3. With Vref changed by hardware. Figure 4. Switching frequency vs. values of R and C.
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MULTIWATT15 PACKAGE MECHANICAL DATA
DIM. MIN. A B C D E F G G1 H1 H2 L L1 L2 L3 L4 L7 M M1 S S1 Dia1 21.9 21.7 17.65 17.25 10.3 2.65 4.25 4.63 1.9 1.9 3.65 4.55 5.08 17.5 10.7 22.2 22.1 0.49 0.66 1.02 17.53 19.6 20.2 22.5 22.5 18.1 17.75 10.9 2.9 4.85 5.53 2.6 2.6 3.85 0.862 0.854 0.695 0.679 0.406 0.104 0.167 0.182 0.075 0.075 0.144 0.179 0.200 0.689 0.421 0.874 0.870 1.27 17.78 1 0.55 0.75 1.52 18.03 0.019 0.026 0.040 0.690 0.772 0.795 0.886 0.886 0.713 0.699 0.429 0.114 0.191 0.218 0.102 0.102 0.152 0.050 0.700 mm TYP. MAX. 5 2.65 1.6 0.039 0.022 0.030 0.060 0.710 MIN. inch TYP. MAX. 0.197 0.104 0.063
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Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of SGS-THOMSON Microelectronics. (c) 1994 SGS-THOMSON Microelectronics - All Rights Reserved SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco - The Netherlands - Singapore Spain - Sweden - Switzerland - Taiwan - Thaliand - United Kingdom - U.S.A.
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