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L6567
HIGH VOLTAGE DRIVER FOR CFL
n n n
BCD-OFF LINE TECHNOLOGY FLOATING SUPPLY VOLTAGE UP TO 570V GND REFERRED SUPPLY VOLTAGE UP TO 18V UNDER VOLTAGE LOCK OUT CLAMPING ON Vs DRIVER CURRENT CAPABILITY: 30mA SOURCE 70mA SINK PREHEAT AND FREQUENCY SHIFT TIMING
MULTIPOWER BCD TECHNOLOGY
n n n
SO14
DIP14
n
ORDERING NUMBERS: L6567D L6567
DESCRIPTION The device is a monolithic high voltage integrated circuit designed to drive CFL and small TL lamps with a minimum part count. It provides all the necessary functions for proper preheat, ignition and steady state operation of the lamp: variable frequency oscillator;
settable preheating and ignition time; capacitive mode protection; lamp power independent from mains voltage variation.
Besides the control functions, the IC provides the level shift and drive function for two external power MOS FETs in a half-bridge topology.
BLOCK DIAGRAM
Vhv Rhv RHV 13 VS 5 Cp/Cav CP 8 1 FS Vhv
VS HIGH SIDE DRIVER
FEED FORWARD
PREHEATING TIMING
LEVEL SHIFTING
2
G1
Cboot
T1 L
Chv Lamp
CF
12 VCO + FREQ. SHIFTING LOGIC VOLTAGE REFERENCE BIAS CURRENT GENERATOR to comp. 10 Ref RREF C LOW SIDE DRIVER
3
S1
CI CS Cf Ci
14
6
G2
T2
CL
MAINS Chv
7 11
PGND SGND
Rshunt
9
RS
D96IN441B
January 2000
This is preliminary information on a new product now in development. Details are subject to change without notice.
1/15
L6567
PIN FUNCTION
N 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Pin FS G1 S1 NC VS G2 PGND CP RS RREF SGND CF RHV CI Floating Supply of high side driver Gate of high side switch Source of high side switch High Voltage Spacer. (Should be not connected) Supply Voltage for GND level control and drive Gate of low side switch Power Ground First timing (TPRE TIGN), then averaging the ripple in the representation of the HVB (derived through RHV). R SHUNT: current monitoring input Reference resistor for current setting Signal Ground. Internally Connected to PGND Frequency setting capacitor Start-up supply resistor, then supply voltage sensing. Timing capacitor for frequency shift Description
PIN CONNECTION (Top view)
FS G1 S1 N.C. VS G2 PGND
1 2 3 4 5 6 7
D96IN440
14 13 12 11 10 9 8
CI RHV CF SGND RREF RS CP
2/15
L6567
ABSOLUTE MAXIMUM RATINGS
Symbol VS VRHV VCP VCF VCI VRREF VRS Low Voltage Supply Mains Voltage Sensing Preheat/Averaging Oscillator Capacitor Voltage Frequency Shift Capacitor Voltage Reference Resistor Voltage Current Sense Input Voltage transient 50ns VG2 V S1 Low Side Switch Gate Output High Side Switch Source Output: normal operation 0.5sec mains transient VG1 High Side Switch Gate Output: normal operation 0.5sec mains transient with respect to pin S1 VFS Floating Supply Voltage: normal operation 0.5sec mains transient VFS/S1 VFS/T V S1/T IRHV IVs Tstg Tj Floating Supply vs S1 Voltage VFS Slew Rate (Repetitive) VS1 Slew Rate (Repetitive) Current Into RHV Clamped Current into VS Storage Temperature Junction Temperature Parameter Value 18 (1) VS +2VBE (2) 5 5 5 5 -5 to 5 -15 18 -1 to 373 -1 to 550 -1 to 391 -1 to 568 Vbe to V S 391 568 18 -4 to 4 -4 to 4 3 (3) 200 (4) -40 to 150 -40 to 150 V V V V V V V V V V V V V V V V/ns V/ns mA mA C C Unit V
NOTES: (1) Do not exceed package thermal dissipation limi ts (2) For VS VS high 1 (3) For VS > VS high 1 (4) Internally Limited Note: ESD immunity for pins 1, 2 and 3 is guaranteed up to 900 V (Human Body Model)
3/15
L6567
ELECTRICAL CHARACTERISTCS (VS = 12V; RREF = 30K; CF = 100pF; Tj = 25C; unless otherwise specified.)
Symbol Parameter Test Conditio n Min. Typ. Max. Unit
VS - SUPPLY VOLTAGE SECTION VS high 1 VS high2 V S low 2 VS HYST V S low 1 ISSP ISOP VS Turn On Threshold VS Clamping Voltage VS Turn Off Threshold Supply Voltage Hysteresis VS Voltage to Guarantee VG1 ="0"and VG2 = "1 VS Supply Current at Start Up VS Supply Operative Current VS = 10.6V Before turn on VS = VShigh 1 VS = 20mA 10.7 12 9 1.5 1 11.7 13 10 1.65 12.7 14 11 1.8 6 V V V V V
50
250 1.2
mA mA
OSCILLATOR SECTION fosc min fosc 600m fosc 1mA fosc max
ICF/VCI
Minimum Oscillator frequency Feed Forward Frequency Feed Forward Frequency
IRHV = 0mA; CI = 5V IRHV = 600mA IRHV = 1mA
41.7 47.88 79.8 96.75 9
43 50.4 84 107.5
44.29 52.92 88.2 118.25 17.5
kHz kHz kHz KHz A/V
Maximum Oscillator Frequency CI = 0V Oscillator Transconductance
PREHEAT/IGNITION SECTION P.H.T. P.H.clocks IGN.clocks Preheat Time Number of Preheat Clocks Number of Ignition Clocks Cp = 150nF 0.88 1 16 15 1.12 sec
RATE OF FREQUENCY CHANGE SECTION ICIP charge ICII charge ICI disch VTH CI CI Charging Current During Preheat CI Charging Current During Ignition CI Discharge Current CI Low Voltage Threshold 106 1 -52 10 118 1.2 -47 130 1.4 -42 100 mA mA mA mV
RS - THRESHOLD SECTION VCMTH VPH Capacitive Mode Voltage Threshold Preheat Voltage Threshold 0 -0.64 20 -0.6 40 -0.56 mV V
G1 - G2 DELAY TIMES SECTION G1DON On Delay of G1 Output 1.05 1.4 1.75 s
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L6567
ELECTRICAL CHARACTERISTCS (Continued)
Symbol G2DON Parameter On Delay of G2 Output Test Conditio n Min. 1.05 0.87 0.77 Typ. 1.4 Max. 1.75 1.15 1.30 Unit s
IRHV = 1mA; Cl = 5V G1 DON + G1ON Ratio between Delay Time + ------------------------------------------ Conduction Time of G1 and G2 Cl = 0V G2 DON + G2ON LOW SIDE DRIVER SECTION Ron G2 so Ron G2 si Ron G1 so Ron G1 si G2 Source Output Resistance G2 Sink Output Resistance G1 Source Output Resistance G1 Sink Output Resistance VS = 12V, V = 3V VS = 12V, V = 3V VS = 10V, V = 3V VS = 10V, V = 3V
80 65 80 65
190 125 190 125

HIGH SIDE DRIVER SECTION IFSLK IS1 LK Leakage Current of FS PIN to GND Leakage Current of S1 PIN to GND VFS = 568V; G1 = L VFS = 568V; G1 = H VS1 = 568V; G1 = L VS1 = 568V; G1 = H 5 5 5 5 A A A A
BOOTSTRAP SECTION Boot Th BOOTSTRAP Threshold VS = 10.6V before turn on 5 (*) V
AVERAGE RESISTOR R AVERAGE Average Resistor 27 38.5 50 k
(*) Before starting the first commutation; when switching 6V is guaranteed.
General operation The L6567 uses a small amount of current from a supply resistor(s) to start the operation of the IC. Once start up condition is achieved, the IC turns on the lower MOS transistor of the half bridge which allows the bootstrap capacitor to charge. Once this is achieved, the oscillator begins to turn on the upper and lower MOS transistors at high frequency, and immediately ramps down to a preheat frequency. During this stage, the IC preheats the lamp and after a predetermined time ramps down again until it reaches the final operating frequency. The IC monitors the current to determine if the circuit is operating in capacitive mode. If capacitive switching is detected, the IC increases the output frequency until zero-voltage switching is resumed. Startup and supply in normal operation At start up the L6567 is powered via a resistor connected to the RHV pin (pin 13) from the rectified mains. The current charges the CS capacitor connected to the VS pin (pin 5). When the VS voltage reaches the threshold VS LOW1 (max 6V), the low side MOS transistor is turned on while the high side one is kept off. This condition assures that the bootstrap capacitor is charged. When VS HIGH1 threshold is reached the oscillator starts, and the RHV pin does not provide anymore the supply current for the IC (see fig.1).
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L6567
Figure 1. Start up
VSHIGH1
VSLOW1 VS
0
TDT
VG
low side mosfet 0
VG-VS
high side mosfet
0
CF
0
TIME
Oscillator The circuit starts oscillating when the voltage supply VS has reached the VS HIGH1 threshold. In steady state condition the oscillator capacitor CF (at pin 12) is charged and discharged symmetrically with a current set mainly by the external resistor RREF connected to pin 10. The value of the frequency is determined by capacitor CF and resistor RREF. This fixed value is called FMIN. A dead time TDT between the ON phases of the transistors is provided for avoiding cross conduction, so the duty cycle for each is less than 50%. The dead time depends on RREF value (fig. 7). The IC oscillating frequency is between FMIN and FMAX = 2.5 * FMIN in all conditions. Preheating mode The oscillator starts switching at the maximum frequency FMAX. Then the frequency decreases at once to reach the programmed preheating frequency (fig.2). The rate of decreasing (df/dt) is determined by the external capacitor CI (pin 14). The preheat time TPRE is adjustable with external components (RREF and CP). The preheat current is adjusted by sense resistance RSHUNT. During the preheating time the load current is sensed with the sense resistor RSHUNT (connected between pin 9-RS- and pin 7-PGND-). At pin 9 the voltage drop on RSHUNT is sensed at the moment the low side MOS FET is turned off. There is an internal comparator with a fixed threshold VPH: if VRS > VPH the frequency is decreased and if VRS < VPH the frequency is increased. If the VPH threshold is reached, the frequency is held constant for the programmed preheating time TPRE. TPRE is determined by the external capacitor CP (pin8) and by the resistor RREF: CP is charged 16 times with a current that depends on RREF, and these 16 cycles determine the TPRE. So the preheat mode is programmable with external components as far as TPRE is concerned (RREF &CP) and as far as the preheating current is concerned (choosing properly RSHUNT and the resonant load components: L and C L). The circuit is held in the preheating mode when pin 8 (CP) is grounded. In case FMIN is reached during preheat, the IC assumes an open load. Consequently the oscillation stops with
the low side MOS transistor gate on and the high side gate off. This condition is kept until V undershoots VS LOW1. S
6/15
L6567
Figure 2. Preheating and ignition state.
FREQUENCY FMAX
FMIN
preheating state ignition state burning state
TIME
Ignition mode At the end of the preheat phase the frequency decreses to the minimum frequency (FMIN), causing an increased coil current and a high voltage appearing across the lamp. That is because the circuit works near resonance. This high voltage normally ignites the lamp. There is no protection to avoid high ignition currents through the MOS transistors when the lamp doesn't ignite. This only occurs in an end of lamp life situation in which the circuit may break. Now the lowest frequency is the resonance frequency of L and CL (the capacitor across the lamp). The ignition phase finishes when the frequency reaches FMIN or (at maximum) when the ignition time has elapsed. The ignition time is related to TPRE: TIGN = (15/16) * TPRE. The CP capacitor is charged 15 times with the same current used to charge it during TPRE. The frequency shifting slope is determined by CI. During the ignition time the VRS monitoring function changes in the capacitive mode protection. Steady state operation: feed forward frequency The lamp starts operating at FMIN, determined by RREF and CF directly after the ignition phase. To prevent too high lamp power at high mains voltages, a feed forward correction is implemented. At the end of the preheat phase the RHV pin is connected to an internal resistor to sense the High Voltage Bus. If the current in this resistor increases and overcomes a value set by RREF , the current that charges the oscillator capacitor CF increases too. The effect is an increase in frequency limiting the power in the lamp. In order to prevent feed forward of the ripple of the VHV voltage, the ripple is filtered with capacitor CP on pin 8 and an integrated resistor RAVERAGE.
Figure 3. Burn state
FREQUENCY
feed forward mode FMIN Irhv
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L6567
Capacitive mode protection During ignition and steady state the operating frequency is higher than the resonance frequency of the load (L,CL,RLAMP and RFILAMENT), so the transistors are turned on during the conduction time of the body diode in order to maintain Zero Voltage Switching. If the operating frequency undershoots the resonance frequency ZVS doesn't occur and causes hard switching of the MOS transistors. The L6567 detects this situation by measuring VRS when the low side MOS FET is turned on. At pin 9 there is an internal comparator with threshold V TH (typ~20mV ): if VRS < VCM TH capacitive mode is CM assumed and the frequency is increased as long as this situation is present. The shift is determined by CI. Steady state frequency At any time during steady state the frequency is determined by the maximum on the following three frequencies:
, fSTEADY STATE= MAX {FMIN, fFEED FORWARD fCAPACITIVE MODE PROTECTION}.
IC supply At start up the IC is supplied with a current that flows through RHV and an internal diode to the VS pin whichcharges the external capacitor CS. In steady state condition RHV is used as a mains voltage sensor, so it doesn't provide anymore the supply current. The easiest way to charge the CS capacitor (and to supply the IC) is to use a charge pump from the middle point of the half bridge. To guarantee a minimum gate power MOS drive, the IC stops oscillating when VS is lower than VS HIGH2. It will restart once the VS will become higher than VS HIGH1. A minimum voltage hysteresis is guaranteed. The IC restarts operating at f = FMAX ,then the frequency shifts towards FMIN. The timing of this frequency shifting is TIGN (that is: CP capacitor is charged and discharged 15 times).Now the oscillator frequency is controlled as in standard burning condition (feed forward and capacitive mode control). Excess charge on CS is drained by an internal clamp that turns on at voltage VS CL . Ground pins Pin 7(PGND) is the ground reference of the IC with respect to the application. Pin 11( SGND) provides a local signal ground reference for the components connected to the pins CP, CI, RREF and CF. Relationship between external components and sistem working condition L6567 is designed to drive CFL and TL lamps with a minimum part count topology. This feature implies that each external component is related to one or more circuit operating state. This table is a short summary of these relationships: FMIN ---> RREF & CF FFEED FORWARD ---> CF & IRHV TPRE & TIGN ---> CP & RREF FPRE ---> RSHUNT, L, CL, LAMP TDT ---> RREF df/dt ---> CI Some useful formulas can well approximate the values: 1 ---------------F MI N ----------------8 RR E F CF
If IRHV is greater than: I R HV ------------- , the feed forward frequency is settled and the frequency value is fitted by the R R EF followi ng expression: IR H V F F E ED FOR W AR D --------------------121 CF
15
8/15
L6567
Other easy formulas fit rather well: TDT 46.75 * 10^-12 * RREF TPRE 224 * CP * RREF As far as df/dt is concerned, there are no easy formulas that fit the relation between CF, RF, and CI. CI is charged and discharged by three different currents that are derived from different mirroring ratios by the current flowing on RREF. The voltage variations on CI are proportional to the current that charges CF, that is to say they are proportional to df/dt. The values obtained in the testing conditions (CI = 100nF) are: during preheating and working conditions the typical frequency increase is ~ 20KHz/ms, the typical decrease is ~-10Khz/ms; During ignition the frequency variation is ~ -200Hz/ms. If slower variations are needed, CI has to be increased. Due to these tight relationships, it is recommended to follow a precise procedure: first RHV has to be chosen looking at startup current needs and dissipation problems. Then the feed forward frequency range has to be determined, and so CF is set. Given a certain CF, RREF is set in order to fix FMIN. Now CP can be chosed to set the desired TPRE and TIGN. The other external parameters (RSHUNT and CI) can be chosen at the end because they are just related to a single circuit parameters.
9/15
L6567
Figure 4. IC Operation
START
VS>VSLOW1
Y
N
NO OSCILLATION LOW SIDE MOS ON HIGH SIDE MOS OFF
N
VS>VSHIGH1
Y
START OSCILLATION F=FMAX T=T0 VS>VSHIGH2
N N Y
VS>VSHIGH2
Y
T>T0+TPRE+TIGN
Y Y N
T=T0+TPRE
N
VRSPREHEATING MODE
IGNITION MODE
Y
N
Y
N
VRS>VPH
N
F>FMIN
Y
INCREA SE FREQUENCY
F>FMIN
Y
INCREASE FREQUE NCY
DECR EASE FREQUENCY
DECREA SE FREQUE NCY
OPEN LOAD DETECT ION: STOP LOW SIDE MOS ON AND HIGH SIDE MOS OFF
N
FEED FORWARD MODE ACTIVATED
VS>VSHIGH2
Y
STOP OSCILLATION LOW SIDE MOS ON HIGH SIDE MOS OFF
VRSY
BURNING MODE
N Y
F>FFEEDFORWARD
N
VS>VSHIGH1
Y
N
N
F>FMIN
Y
INCR EASE FREQUENCY
RESTART WITH F=FMAX FREQUENCY SHIFTS IN T=TIGN TOWARDS BURNING STATE CONDITION (F=MAX{FMAX,FFEEDFORWARD,FCAPACITIVEMODE})
DECREA SE FREQUE NCY
10/15
L6567
Figure 5. Working frequency vs I HV R @ RREF = 30Kohm
1 6 0 .0 0
15 0 .0 0 14 0 .0 0 13 0 .0 0
Figure 8. Frequency vs IRHV @ CF = 82pF
120.00
R re f= 30Ko hm
C f= 47pF
Cf= 56p F
100.00
1 2 0 .0 0
11 0 .0 0
Cf= 6 8p F C f= 82pF
fr eq u e n cy [kH z]
10 0 .0 0 9 0 .0 0
fr e q u e n c y [k H z ]
80.00
R r ef= 20 K R r ef= 22 K R re f= 24K
Cf= 100 pF Cf= 120 pF
8 0 .0 0
7 0 .0 0 6 0 .0 0 5 0 .0 0
Cf=15 0pF Cf=1 80 pF Cf=22 0pF
60.00
R re f=2 7K R re f= 30 K R re f= 33K
4 0 .0 0
3 0 .0 0
40.00
2 0 .0 0 1 0 .0 0
Rr ef= 36 K R re f= 39 K , 4 3 K, 4 7K , 5 1K
0 .0 0 0.2 0
0.20
0.4 0 0 .6 0 0 .8 0 1 .00 1 .20
0.40
0 .60 0.80 Irh v [m A ]
1.00
1.20
Irh v [m A ]
Figure 6. Frequency vs C @ RREF=30Kohm F
1 60 .0 0
150.00 140.00 130.00
Figure 9. Frequency vs IRHV @ CF=100pF
10 0.0 0
R ref= 30K ohm
8 0.0 0
1 20 .0 0
110.00
fre q u e n c y [k H z ]
100.00 90.00
fr e q u e n c y [k H z ]
R re f= 2 0 K
6 0.0 0
R r ef = 2 2 K Rr ef = 2 4 K R re f = 2 7 K R re f = 3 0 K
80 .0 0
70.00 60.00 50.00
4 0.0 0
I=1m A
R re f = 3 3 K R re f = 3 6 K R re f = 3 9K ,4 3 K
40 .0 0
30.00 20.00 10.00
I= 0 .7 5 m A )
I=0.5m A
0 .0 0 40 .0 0
2 0.0 0 0 .2 0
60 .0 0
0 .4 0
0 .6 0
0 .8 0
1 .0 0
1 .2 0
80 .0 0 1 00 .0 0 1 2 0.00 14 0 .0 0 16 0.0 0 1 80 .0 0 20 0.0 0 2 20 .0 0 2 4 0.00
Ir h v [m A ]
C f [p F ]
Figure 7. TDT vs RREF @ CF = 100pF
T d t [ca lc u late d da ta] 2.40
Figure 10. Frequency vs IRHV @ CF=120pF
80 .0 0
Td t [m e as u re d d a ta] 2.00 60 .0 0
fre q u e n c y [k H z ]
R r ef = 20 K
T d t [u s ]
1.60
R re f = 2 2 K R r e f = 24 K
40 .0 0
R re f = 2 7 K R re f= 3 0 K
1.20
R r e f = 33 K R re f = 3 6 K R re f = 3 9 K
R r e f= 43 K , 4 7 K , 5 1 K
0.80 20 .00
30 .00
4 0.0 0
50.00
6 0.0 0
20 .0 0 0 .20
0 .40
0.60
0.80
1.00
1.20
R re f [ K o h m ]
Ir h v [m A ]
11/15
L6567
Figure 11. Frequency vs IRHV @ CF= 150pF
80.00
120000.00
Figure 13. FFEED FORWARD: measurements and calculations
c a lc u latio ns ( 1/12 1 )*Ir hv /C f
110000.00
Cf= 8 2pF m eas u re m en ts
100000.00
Cf= 1 00p F
90000.00
60.00 F req . fe ed for wa rd [H z]
80000.00
C f= 12 0 pF
70000.00
fre q u e n c y [k H z ]
60000.00 50000.00
Cf= 1 50p F
R ref= 20 K
40.00
R ref= 22 K Rr ef= 24 K R re f= 27K R re f= 30K R r ef= 33K Rr ef= 36 K R r ef= 39K
40000.00 30000.00 20000.00
20.00
Rr ef=4 3 K, 47K , 51 K
10000.00 0.00 0. 4 0
0 .6 0
0 .8 0
1 . 00
1 .2 0
Irh v [ m A ] 0.20 0.40 0.60 0.80 Ir h v [m A ] 1.00 1.20
Figure 12. FMIN: measurements and calculations
1 00 .0 0
m eas ura m ents Fm in= 1/(8 *C f*R ref)
80 .0 0
F m in [KH z ]
60 .0 0
40 .0 0
C f= 82pF C f=100p F C f=120pF
20 .0 0
C f=15 0pF
0 .0 0 20 .0 0 30 .0 0 4 0 .0 0 50 .0 0
R re f [K o hm ]
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L6567
DIM. MIN. a1 B b b1 D E e e3 F I L Z 1.27 0.51 1.39
mm TYP. MAX. MIN. 0.020 1.65 0.5 0.25 20 8.5 2.54 15.24 7.1 5.1 3.3 2.54 0.050 0.055
inch TYP. MAX.
OUTLINE AND MECHANICAL DATA
0.065 0.020 0.010 0.787 0.335 0.100 0.600 0.280 0.201 0.130
DIP14
0.100
13/15
L6567
DIM. MIN.. A a1 a2 b b1 C c1 D (1) E e e3 F (1) G L M S 3.8 4.6 0.4 8.55 5.8 0.35 0.19 0.1
mm TYP. MAX.. MIN.. 1.75 0.25 1.6 0.46 0.25 0.5 45 (typ.) 8.75 6.2 1.27 7.62 4 5.3 1.27 0.68 8 (max.) 0.150 0.181 0.016 0.336 0.228 0.014 0.007 0.004
inch TYP.. MAX.. 0.069 0.009 0.063 0.018 0.010 0.020
OUTLINE AND MECHANICAL DATA
0.344 0.244 0.050 0.300 0.157 0.209 0.050 0.027
SO14
(1) D and F do not include mold flash or protrusions. Mold flash or potrusions shall not exceed 0.15mm (.006inch).
14/15
L6567
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. N o license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications 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 (R) 1999 STMicroelectronics - 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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