L296 L296P
HIGH CURRENT SWITCHING REGULATORS
. . . . . . . . . . . . .
4 A OUTPUT CURRENT 5.1 V TO 40 V OUTPUT VOLTAGE RANGE 0 TO 100 % DUTY CYCLE RANGE PRECISE (2 %) ON-CHIP REFERENCE SWITCHING FREQUENCY UP TO 200 KHz VERY HIGH EFFICIENCY (UP TO 90 %) VERY FEW EXTERNAL COMPONENTS SOFT START RESET OUTPUT EXTERNAL PROGRAMMABLE LIMITING CURRENT (L296P) CONTROL CIRCUIT FOR CROWBAR SCR INPUT FOR REMOTE INHIBIT AND SYNCHRONUS PWM THERMAL SHUTDOWN
M u lt i w a tt (15 lead) OR D E R I N G NUMBERS : L2 9 6 (Vertical) L 2 96 H T (Horizontal) L2 9 6 P (Vertical) L 2 96 P H T (Horizontal)
D ES C R I P T I O N The L296 and L296P are stepdown power switching regulators delivering 4 A at a voltage variable from 5.1 V to 40 V. Features of the devices include soft start, remote inhibit, thermal protection, a reset output for microprocessors and a PWM comparator input for synchronization in multichip configurations. The L296P incudes external programmable limiting current. PI N CONNECTION (top view)
The L296 and L296P are mounted in a 15-lead Multiwatt plastic power package and requires very few external components. Efficient operation at switching frequencies up to 200 KHz allows a reduction in the size and cost of external filter components. A voltage sense input and SCR drive output are provided for optional crowbar overvoltage protection with an external SCR.
June 2000
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PIN FUNCTIONS
N 1 Function Voltage Sense Input for Crowbar Overvoltage Protection. Normally connected to the feedback input thus triggering the SCR when V out exceeds nominal by 20 %. May also monitor the input and a voltage divider can be added to increase the threshold. Connected to ground when SCR not used. OUTPUT Regulator Output SUPPLY VOLTAGE Unrergulated Voltage Input. An internal Regulator Powers the L296s Internal Logic. CURRENT LIMIT A resistor connected between this terminal and ground sets the current limiter threshold. If this terminal is left unconnected the threshold is internally set (see electrical characteristics). SOFT START Soft Start Time Constant. A capacitor is connected between this terminal and ground to define the soft start time constant. This capacitor also determines the average short circuit output current. INHIBIT INPUT TTL Level Remote Inhibit. A logic high level on this input disables the device. SYNC INPUT Multiple L296s are synchronized by connecting the pin 7 inputs together and omitting the oscillator RC network on all but one device. GROUND Common Ground Terminal FREQUENCY A series RC network connected between this terminal and ground determines the COMPENSATION regulation loop gain characteristics. FEEDBACK INPUT The Feedback Terminal on the Regulation Loop. The output is connected directly to this terminal for 5.1V operation ; it is connected via a divider for higher voltages. OSCILLATOR A parallel RC networki connected to this terminal determines the switching frequency. This pin must be connected to pin 7 input when the internal oscillator is used. RESET INPUT Input of the Reset Circuit. The threshold is roughly 5 V. It may be connected to the feedback point or via a divider to the input. RESET DELAY A capacitor connected between this terminal and ground determines the reset signal delay time. RESET OUTPUT Open collector reset signal output. This output is high when the supply is safe. CROWBAR OUTPUT SCR gate drive output of the crowbar circuit. Name CROWBAR INPUT
2 3 4
5
6 7 8 9 10 11 12 13 14 15
BLOCK DIAGRAM
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CIRCUIT OPERATION (refer to the block diagram) The L296 and L296P are monolithic stepdown switching regulators providing output voltages from 5.1V to 40V and delivering 4A. The regulation loop consists of a sawtooth oscillator, error amplifier, comparator and the output stage. An error signal is produced by comparing the output voltage with a precise 5.1V on-chip reference (zener zap trimmed to 2 %). This error signal is then compared with the sawtooth signal to generate the fixed frequency pulse width modulated pulses which drive the output stage. The gain and frequency stability of the loop can be adjusted by an external RC network connected to pin 9. Closing the loop directly gives an output voltage of 5.1V. Higher voltages are obtained by inserting a voltage divider. Output overcurrents at switch on are prevented by the soft start function. The error amplifier output is initially clamped by the external capacitor Css and allowed to rise, linearly, as this capacitor is charged by a constant current source. Output overload protection is provided in the form of a current limiter. The load current is sensed by an internal metal resistor connected to a comparator. When the load current exceeds a preset threshold this comparator sets a flip flop which disables the output stage and discharges the soft start capacitor. A second comparator resets the flip flop when the voltage across the soft start capacitor has fallen to Figure 1 : Reset Output Waveforms 0.4V. The output stage is thus re-enabled and the output voltage rises under control of the soft start network. If the overload condition is still present the limiter will trigger again when the threshold current is reached. The average short circuit current is limited to a safe value by the dead time introduced by the soft start network. The reset circuit generates an output signal when the supply voltage exceeds a threshold programmed by an external divider. The reset signal is generated with a delay time programmed by an external capacitor. When the supply falls below the threshold the reset output goes low immediately. The reset output is an open collector. The scrowbar circuit senses the output voltage and the crowbar output can provide a current of 100mA to switch on an external SCR. This SCR is triggered when the output voltage exceeds the nominal by 20%. There is no internal connection between the output and crowbar sense input therefore the crowbar can monitor either the input or the output. A TTL - level inhibit input is provided for applications such as remote on/off control. This input is activated by high logic level and disables circuit operation. After an inhibit the L296 restarts under control of the soft start network. The thermal overload circuit disables circuit operation when the junction temperature reaches about 150 C and has hysteresis to prevent unstable conditions.
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Figure 2 : Soft Start Waveforms
Figure 3 : Current Limiter Waveforms
ABSOLUTE MAXIMUM RATINGS
Symbol Vi Vi V2 V2 V1, V12 V15 V4, V5, V7, V9, V13 V10, V6 V14 I9 I11 I14 Ptot Tj, Tstg Input Voltage (pin 3) Input to Output Voltage Difference Output DC Voltage Output Peak Voltage at t = 0.1 sec f = 200KHz Voltage at Pins 1, 12 Voltage at Pin 15 Voltage at Pins 4, 5, 7, 9 and 13 Voltage at Pins 10 and 6 Voltage at Pin 14 (I14 1 mA) Pin 9 Sink Current Pin 11 Source Current Pin 14 Sink Current (V14 < 5 V) Power Dissipation at Tcase 90 C Junction and Storage Temperature Parameter Value 50 50 1 7 10 15 5.5 7 Vi 1 20 50 20 40 to 150 mA mA mA W C Unit V V V V V V V V
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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
ELECTRICAL CHARACTERISTICS (refer to the test circuits Tj = 25oC, Vi = 35V, unless otherwise specified)
Symbol Parameter Test Conditions Min. Typ. Max. Unit Fig. DYNAMIC CHARACTERISTICS (pin 6 to GND unless otherwise specified) Vo Vi Vi Vo Vo Output Voltage Range Input Voltage Range Input Voltage Range Line Regulation Load Regulation Vi = 46V, Io = 1A Vo = Vref to 36V, Io 3A Note (1), Vo = VREF to 36V Io = 4A Vi =10V to 40V, Vo = Vref, Io = 2A Vo = Vref Io = 2A to 4A Io = 0.5A to 4A 5 Tj = 0C to 125C, Io = 2A Io = 4A Io = 2A L296 - Pin 4 Open, Vi = 9V to 40V, Vo = Vref to 36V L296P - Vi = 9V to 40V, Vo = Vref Pin 4 Open RIim = 22k ISH Input Average Current Efficiency Vi = 46V, Output Short-circuited Io = 3 A Vo = Vref Vo = 12V Vi = 2 Vrms, fripple = 100Hz Vo = Vref, Io = 2A Vi = 9V to 46V Tj = 0C to 125C Vo = Vref, Io = 1A Note (2) 200 135 145 50 85 4.5 15 10 15 5.1 0.4 2 1.3 3.2 2.1 7.5 Vref 9 40 46 46 50 30 45 5.2 V mV/C V V A A 5 2.5 60 75 85 56 100 0.5 1 115 dB kHz % % kHz C 4 4 4 4 7 4.5 100 mA % 4 4 4 4 4 4 4 V V V mV mV 4 4 4 4 4
Vref Vref T Vd I2L
Internal Reference Voltage (pin 10) Vi = 9V to 46V, Io = 2A Average Temperature Coefficient of Reference Voltage Dropout Voltage Between Pin 2 and Pin 3 Current Limiting Threshold (pin 2)
SVR f f Vi f Tj fmax Tsd
Supply Voltage Ripple Rejection Switching Frequency Voltage Stability of Switching Frequency Temperature Stability of Switching Frequency Maximum Operating Switching Frequency Thermal Shutdown Junction Temperature
DC CHARACTERISTICS I3Q Quiescent Drain Current Vi = 46V, V7 = 0V, S1 : B, S2 : B V6 = 0V V6 = 3V Vi = 46V, V6 = 3V, S1 : B, S2 : A, V7 = 0V mA 66 30 85 40 2 mA
I2L
Note
Output Leakage Current
(1) : Using min. 7 A schottky diode. (2) : Guaranteed by design, not 100 % tested in production.
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ELECTRICAL CHARACTERISTICS (continued)
Symbol SOFT START I5 so I5 si INHIBIT V6 L V6H Input Voltage Low Level High Level Input Current with Input Voltage Low Level High Level Vi = 9V to 46V, V7 = 0V, S1 : B, S2 : B Vi = 9V to 46V, V7 = 0V, S1 : B, S2 : B V6 = 0.8V V6 = 2V V 0.3 2 0.8 5.5 A 10 3 6a 6a Source Current Sink Current V6 = 0V, V5 = 3V V6 = 3V, V5 = 3V 80 50 130 70 150 120 A A 6b 6b Parameter Test Conditions Min. Typ. Max. Unit Fig.
I6L I6H
ERROR AMPLIFIER V9H V9L I9 si I9 so I10 Gv High Level Output Voltage Low Level Output Voltage Sink Output Current Source Output Current Input Bias Current DC Open Loop Gain V10 = 4.7V, I9 = 100A, S1 : A, S2 : A V10 = 5.3V, I9 = 100A, S1 : A, S2 : E V10 = 5.3V, S1 : A, S2 : B V10 = 4.7V, S1 : A, S2 : D V10 = 5.2V, S1 : B V10 = 6.4V, S1 : B, L296P V9 = 1V to 3V, S1 : A, S2 : C 46 100 100 150 150 2 2 55 10 10 3.5 0.5 V V A A A A dB A mA 6c 6c 6c 6c 6c 6c 6c
OSCILLATOR AND PWM COMPARATOR I7 I1 1 RESET V12 R V12 F V13 D V13 H V14 S I12 I13 so I13 si I14 Rising Threshold Voltage Falling Threshold Voltage Delay Thershold Voltage Delay Threshold Voltage Hysteresis Output Saturation Voltage Input Bias Current Delay Source Current Delay Sink Current Output Leakage Current V12 = 5.3V, S1 : A, S2 : B I14 = 16mA, V12 = 4.7V, S1, S2 : B V12 = 0V to Vref, S1 : B, S2 : B V13 = 3V, S1 : A, S2 : B V12 = 5.3V V12 = 4.7V Vi = 46V, V12 = 5.3V, S1 : B, S2 : A 70 10 1 110 Vi = 9V to 46V, S1 : B, S2 : B Vref Vref -150mV -100mV 4.75 4.3 Vref -50mV V V V mV 0.4 3 140 100 V A A mA A V V A mA 6d 6d 6d 6d 6d 6d 6d Input Bias Current of PWM Comparator Oscillator Source Current V7 = 0.5V to 3.5V V11 = 2V, S1 : A, S2 : B 5 5 6a
Vref Vref -150mV -100mV 4.5 100 4.7
6d
CROWBAR V1 V15 I1 I1 5 Input Threshold Voltage Output Saturation Voltage Input Bias Current Output Source Current S1 : B Vi = 9V to 46V, Vi = 5.4V, I15 = 5mA, S1 : A V1 = 6V, S1 : B Vi = 9V to 46V, V1 = 6.5V, V15 = 2V, S1 : B 70 100 5.5 6 0.2 6.4 0.4 10 6b 6b 6b 6b
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Figure 4 : Dynamic Test Circuit
C7, C8 : EKR (ROE) L1 : L = 300 H at 8 A
Core type : MAGNETICS 58930 - A2 MPP N turns : 43 Wire Gauge : 1 mm (18 AWG) COGEMA 946044 (*) Minimum suggested value (10 F) to avoid oscillations. Ripple consideration leads to typical value of 1000 F or higher.
Figure 5 : PC. Board and Component Layout of the Circuit of Figure 4 (1:1 scale)
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Figure 6 : DC Test Circuits. Figure 6a. Figure 6b.
Figure 6c.
1 - Set V10 FOR V9 = 1 V 2 - Change V10 to obtain V9 = 3 V 3 - GV = DV9 V10 = 2V V10
Figure 6d.
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Figure 7 : Quienscent Drain Current vs. Supply Voltage (0 % Duty Cycle - see fig. 6a). Figure 8 : Quienscent Drain Current vs. Supply Voltage (100 % Duty Cycle see fig. 6a).
Figure 9 : Quiescent Drain Current vs. Junction Temperature (0 % Duty Cycle see fig. 6a).
Figure 10 : Quiescent Drain Current vs. Junction Temperature (100 % Duty Cycle see fig. 6a).
Figure 11 : Reference Voltage (pin 10) vs. VI (see fig. 4).
Figure 12 : Reference Voltage (pin 10) vs. Junction Temperature (see fig. 4).
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Figure 13 : Open Loop Frequency and Phase Response of Error Amplifier (see fig. 6c). Figure 14 : Switching Frequency vs. Input Voltage (see fig. 4).
Figure 15 : Switching Frequency vs. Junction Temperature (see fig. 4).
Figure 16 : Switching Frequency vs. R1 (see fig. 4).
Figure 17 : Line Transient Response (see fig. 4).
Figure 18 : Load Transient Response (see fig. 4).
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Figure 19 : Supply Voltage Ripple Rejection vs. Frequency (see fig. 4). Figure 20 : Dropout Voltage Between Pin 3 and Pin 2 vs. Current at Pin 2.
Figure 21 : Dropout Voltage Between Pin 3 and Pin 2 vs. Junction Temperature.
Figure 22 : Power Dissipation Derating Curve.
Figure 23 : Power Dissipation (device only) vs. Input Voltage.
Figure 24 : Power Dissipation (device only) vs. Input voltage.
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Figure 25 : Power Dissipation (device only) vs. Output Voltage (see fig. 4). Figure 26 : Power Dissipation (device only) vs. Output Voltage (see fig. 4).
Figure 27 : Voltage and Current Waveforms at Pin 2 (see fig. 4).
Figure 28 : Efficiency vs. Output Current.
Figure 29 : Efficiency vs. Output Voltage.
Figure 30 : Efficiency vs. Output Voltage.
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Figure 31 : Current Limiting Threshold vs. Rpin 4 (L296P only). Figure 32 : Current Limiting Threshold vs. Junction Temperature.
Figure 33 : Current Limiting Threshold vs. Supply Voltage.
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APPLICATION INFORMATION Figure 34 : Typical Application Circuit.
(*) Minimum value (10 F) to avoid oscillations ; ripple consideration leads to typical value of 1000 F or higher L1 : 58930 - MPP COGEMA 946044 ; GUP 20 COGEMA 946045
SUGGESTED INDUCTOR (L1)
Core Type Magnetics 58930 A2MPP Thomson GUP 20 x 16 x 7 Siemens EC 35/17/10 (B6633& G0500 X127) VOGT 250 H Toroidal Coil, Part Number 5730501800 No Turns 43 65 40 Wire Gauge 1.0 mm 0.8 mm 2 x 0.8 mm Air Gap 1 mm
V0 12 V 15 V 18 V 24 V
Resistor Values for Standard Output Voltages R8 4.7 K 4.7 K 4.7 K 4.7 K
R7 6.2 K 9.1 K 12 K 18 K
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Figure 35 : P.C. Board and Component Layout of the Circuit of fig. 34 (1:1 scale)
SELECTION OF COMPONENT VALUES (see fig. 34)
Component R1 R2 Recommended Value 100 k Purpose Set Input Voltage Threshold for Reset. Allowed Rage Notes Min. Max. Vi min -1 220k R1/R2 5 If output voltage is sensed R1 and R2 may be limited and pin 12 connected to pin 10. 1 k 100k 22k May be omitted and pin 6 grounded if inhibit not used. 10k VO Omitted if reset function not used.
R3 R4 R5 R6 R7 R8 Riim C1 C2 C3 C4 C5 C6 C7, C8 L1 Q1
4.3 k 10 k 15 k
Sets Switching Frequency Pull-down Resistor Frequency Compensation Collector Load For Reset Output Divider to Set Output Voltage Sets Current Limit Level Stability Sets Reset Delay Sets Switching Frequency Soft Start Frequency Compensation High Frequency Compensation Output Filter Crowbar Protection
0.05A
7.5k 2.2F 1 nF 1 F 1k VO - VREF VREF If Riim is omitted and pin 4 left open the current limit is internally fixed. R7/R8 = Omitted if reset function not used. Also determines average short circuit current. Not required for 5 V operation.
4.7 k 10 F 2.2 F 2.2 nF 2.2 F 33 nF 390 pF 100 F 300 H
3.3nF
100H
D1
Recirculation Diode
The SCR must be able to withstand the peak discharge current of the output capacitor and the short circuit current of the device. 7A Schottky or 35 ns trr Diode. 15/22
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Figure 36 : A Minimal 5.1 V Fixed Regulator. Very Few Components are Required.
Figure 37 : 12 V/10 A Power Supply.
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Figure 38 : Programmable Power Supply.
V o = 5.1 to 15 V I o = 4 A max. (min. load current = 100 mA) ripple 20 mV load regulation (1 A to 4 A) = 10 mV (V o = 5.1 V) line regulation (220 V 15 % and to I o = 3 A) = 15 mV (V o = 5.1 V)
Figure 39 : Preregulator for Distributed Supplies.
(*) L2 and C2 are necessary to reduce the switching frequency spikes.
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Figure 40 : In Multiple Supplies Several L296s can be Synchronized As Shown. Figure 41 : Voltage Sensing for Remote Load.
Figure 42 : A 5.1 V/15 V/24 V Multiple Supply. Note the Synchronization of the Three L296s.
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Figure 43 : 5.1V/2A Power Supply using External Limiting Current Resistor and Crowbar Protection on the Supply Voltage (L296P only) sistor may be added, as shown in Figure 45 ; with this circuit discharge times of a few microseconds may be obtained. Figure 45
SOFT-START AND REPETITIVE POWER-ON When the device is repetitively powered-on, the softstart capacitor, CSS, must be discharged rapidly to ensure that each start is "soft". This can be achieved economically using the reset circuit, as shown in Figure 44. In this circuit the divider R1, R2 connected to pin 12 determines the minimum supply voltage, below which the open collector transistor at the pin 14 output discharges CSS. Figure 44
HOW TO OBTAIN BOTH RESET AND POWER FAIL Figure 46 illustrates how it is possible to obtain at the same time both the power fail and reset functions simply by adding one diode (D) and one resistor (R). In this case the Reset delay time (pin 13) can only start when the output voltage is VO VREF - 100mV and the voltage accross R2 is higher than 4.5V. With the hysteresis resistor it is possible to fix the input pin 12 hysteresis in order to increase immunity to the 100Hz ripple present on the supply voltage. Moreover, the power fail and reset delay time are automatically locked to the soft-start. Soft-start and delayed reset are thus two sequential functions. The hysteresis resistor should be In the range of aboit 100k and the pull-up resistor of 1 to 2.2k. Figure 46
The approximate discharge times obtained with this circuit are :
CSS (F) 2.2 4.7 10 tDIS (s) 200 300 600
If these times are still too long, an external PNP tran-
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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
OUTLINE AND MECHANICAL DATA
Multiwatt15 V
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DIM. MIN. A B C E F G G1 H1 H2 L L1 L2 L3 L4 L5 L6 L7 S S1 Dia1 2.65 1.9 1.9 3.65 17.25 10.3 20.57 18.03 2.54 17.5 10.7 5.28 2.38 2.9 2.6 2.6 3.85 0.104 0.075 0.075 0.144 17.75 10.9 0.679 0.406 0.49 0.66 1.14 17.57 19.6 20.2 0.810 0.710 0.100 0.689 0.421 0.208 0.094 0.114 0.102 0.102 0.152 0.699 0.429 1.27 17.78 mm TYP. MAX. 5 2.65 1.6 0.55 0.75 1.4 17.91 0.019 0.026 0.045 0.692 0.772 0.795 0.050 0.700 MIN. inch TYP. MAX. 0.197 0.104 0.063 0.022 0.030 0.055 0.705
OUTLINE AND MECHANICAL DATA
Multiwatt15 H
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Information furnished is believed to be accurate and reliable. However, STMicroelectronics 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 STMicroelectronics. Specification mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics 2000 STMicroelectronics Printed in Italy All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco Singapore - Spain - Sweden - Switzerland - United Kingdom - U.S.A. http://www.st.com
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