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LT3468/LT3468-1/LT3468-2 Photoflash Capacitor Chargers in ThinSOT TM
FEATURES

DESCRIPTIO

Highly Integrated IC Reduces Solution Size Uses Small Transformers: 5.8mm x 5.8mm x 3mm Fast Photoflash Charge Times: 4.6s for LT3468 (0V to 320V, 100F, VIN = 3.6V) 5.7s for LT3468-2 (0V to 320V, 100F, VIN = 3.6V) 5.5s for LT3468-1 (0V to 320V, 50F, VIN = 3.6V) Controlled Input Current: 500mA (LT3468) 375mA (LT3468-2) 225mA (LT3468-1) Supports Operation from Single Li-Ion Cell, or Any Supply from 2.5V up to 16V Adjustable Output Voltage No Output Voltage Divider Needed Charges Any Size Photoflash Capacitor Low Profile (<1mm) SOT-23 Package
The LT(R)3468/LT3468-1/LT3468-2 are highly integrated ICs designed to charge photoflash capacitors in digital and film cameras. A patented control technique* allows for the use of extremely small transformers. Each device contains an on-chip high voltage NPN power switch. Output voltage detection* is completely contained within the device, eliminating the need for any discrete zener diodes or resistors. The output voltage can be adjusted by simply changing the turns ratio of the transformer. The LT3468 has a primary current limit of 1.4A, the LT3468-2 has a 1A limit, and the LT3468-1 has a 0.7A limit. These different current limit levels result in well controlled input currents of 500mA for the LT3468, 375mA for the LT3468-2 and 225mA for the LT3468-1. Aside from the differing current limit, the three devices are otherwise equivalent. The CHARGE pin gives full control of the part to the user. Driving CHARGE low puts the part in shutdown. The DONE pin indicates when the part has completed charging. The LT3468 series of parts are available in tiny low profile (1mm) SOT-23 packages.
, LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Protected by U.S. Patents, including 6518733.
APPLICATIO S

Digital / Film Camera Flash PDA / Cell Phone Flash Emergency Strobe
TYPICAL APPLICATIO
LT3468 Photoflash Charger Uses High Efficiency 4mm Tall Transformer
DANGER HIGH VOLTAGE - OPERATION BY HIGH VOLTAGE TRAINED PERSONNEL ONLY
VIN 2.5V TO 8V 4.7F 2 5 1:10.2 1 4 320V
VIN = 3.6V COUT = 100F
+
100F 100k DONE CHARGE VIN LT3468 DONE CHARGE
346812 TA01
VOUT 50V/DIV AVERAGE INPUT CURRENT 1A/DIV
SW
GND
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LT3468 Charging Waveform
1s/DIV
3468 G01
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LT3468/LT3468-1/LT3468-2
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
ORDER PART NUMBER
TOP VIEW SW 1 GND 2 DONE 3 4 CHARGE 5 VIN
VIN Voltage .............................................................. 16V SW Voltage ................................................ -0.4V to 50V CHARGE Voltage ...................................................... 10V DONE Voltage .......................................................... 10V Current into DONE Pin .......................................... 1mA Maximum Junction Temperature .......................... 125C Operating Temperature Range (Note 2) ...-40C to 85C Storage Temperature Range ..................-65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
LT3468ES5 LT3468ES5-1 LT3468ES5-2 S5 PART MARKING LTAEC LTAGQ LTBCH
S5 PACKAGE 5-LEAD PLASTIC TSOT-23
TJMAX = 125C JA = 150C ON BOARD OVER GROUND PLANE JC = 90C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 3V, VCHARGE = VIN unless otherwise noted. (Note 2) Specifications are for the LT3468, LT3468-1 and LT3468-2 unless otherwise noted.
PARAMETER Quiescent Current Input Voltage Range Switch Current Limit LT3468 (Note 3) LT3468-2 LT3468-1 LT3468, ISW = 1A LT3468-2, ISW = 650mA LT3468-1, ISW = 400mA Measured as VSW - VIN 300ns Pulse Width Measured as VSW - VIN VCHARGE = 3V VCHARGE = 0V VIN = VSW = 5V, in Shutdown

ELECTRICAL CHARACTERISTICS
CONDITIONS Not Switching VCHARGE = 0V
MIN
TYP 5 0
MAX 8 1 16 1.3 0.97 0.65 430 280 200 32 400 80 40 0.1 1 0.3
UNITS mA A V A A A mV mV mV V mV mV A A A V V s V
2.5 1.1 0.77 0.45 1.2 0.87 0.55 330 210 150 31 10 31.5 200 36 15 0 0.01 1 20 3 100 20
Switch VCESAT
VOUT Comparator Trip Voltage VOUT Comparator Overdrive DCM Comparator Trip Voltage CHARGE Pin Current Switch Leakage Current CHARGE Input Voltage High CHARGE Input Voltage Low Minimum Charge Pin Low Time DONE Output Signal High DONE Output Signal Low DONE Leakage Current
HighLowHigh 100k from VIN to DONE 33A into DONE Pin VDONE = 3V, DONE NPN Off
200 100
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT3468E/LT3468E-1/LT3468E-2 are guaranteed to meet performance specifications from 0C to 70C. Specifications over the
-40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process. Note 3: Specifications are for static test. Current limit in actual application will be slightly higher.
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mV nA
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LT3468/LT3468-1/LT3468-2
LT3468 curves use the circuit of Figure 6, LT3468-1 curves use the circuit of Figure 7 and LT3468-2 use the circuit of Figure 8 unless otherwise noted. LT3468 Charging Waveform
VIN = 3.6V COUT = 100F
TYPICAL PERFOR A CE CHARACTERISTICS
VOUT 50V/DIV AVERAGE INPUT CURRENT 1A/DIV
1s/DIV
LT3468 Charge Time
10 9 8 CHARGE TIME (s) CHARGE TIME (s) 7 6 5 4 3 2 1 0 2 3 4 5 6 VIN (V) 7 8 9
3468 G04
TA = 25C
CHARGE TIME (s)
COUT = 100F
COUT = 50F
LT3468 Input Current
800 TA = 25C 400
AVERAGE INPUT CURRENT (mA)
AVERAGE INPUT CURRENT (mA)
600 VIN = 2.8V 400 VIN = 4.2V VIN = 3.6V 200
300 VIN = 2.8V 200 VIN = 4.2V VIN = 3.6V
AVERAGE INPUT CURRENT (mA)
0 0 50 100 150 200 VOUT (V) 250 300
3468 G07
UW
3468 G01
LT3468-1 Charging Waveform
VIN = 3.6V COUT = 50F
LT3468-2 Charging Waveform
VIN = 3.6V COUT = 100F VOUT 50V/DIV
VOUT 50V/DIV AVERAGE INPUT CURRENT 0.5A/DIV
1s/DIV
3468 G02
AVERAGE INPUT CURRENT 0.5A/DIV
1s/DIV
3468 G03
LT3468-1 Charge Time
10 9 8 7 6 5 4 3 2 1 0 2 3 4 5 6 VIN (V) 7 8 9
3468 G05
LT3468-2 Charge Time
10 9 8 7 6 5 4 3 2 COUT = 50F COUT = 100F TA = 25C
TA = 25C
COUT = 50F
COUT = 20F
1 0 2 3
4
6 5 VIN (V)
7
8
9
3468 G06
LT3468-1 Input Current
TA = 25C 600
LT3468-2 Input Current
TA = 25C
450 VIN = 2.8V 300 VIN = 3.6V VIN = 4.2V
100
150
0 0 50 100 150 200 VOUT (V) 250 300
3468 G08
0 0 50 100 150 200 VOUT (V) 250 300
3468 G09
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LT3468/LT3468-1/LT3468-2
LT3468 curves use the circuit of Figure 6, LT3468-1 curves use the circuit of Figure 7 and LT3468-2 use the circuit of Figure 8 unless otherwise noted. LT3468 Efficiency
90 TA = 25C VIN = 4.2V 80
EFFICIENCY (%)
TYPICAL PERFOR A CE CHARACTERISTICS
LT3468-1 Efficiency
90 TA = 25C VIN = 4.2V 80
70
EFFICIENCY (%)
VIN = 3.6V
70
EFFICIENCY (%)
VIN = 2.8V
60
50
40 50 100 150 200 VOUT (V) 250 300
3468 G10
LT3468 Output Voltage
324 323 322 VOUT (V)
VOUT (V)
TA = -40C
VOUT (V)
321 320 319 318 2
TA = 25C TA = 85C
3
4
5 VIN (V)
6
LT3468 Switch Current Limit
1.5 VIN = 3V VOUT = 0V
1.4
ILIM (A)
1.3
ILIM (A)
ILIM (A)
1.2
1.1 -40
-20
0 20 40 60 TEMPERATURE (C)
4
UW
7
3468 G13
LT3468-2 Efficiency
90 TA = 25C VIN = 4.2V VIN = 2.8V 70 VIN = 3.6V
80
VIN = 2.8V VIN = 3.6V
60
60
50
50
40 50 100 150 200 VOUT (V) 250 300
3468 G11
40 50 100 200 150 VOUT (V) 250 300
3468 G12
LT3468-1 Output Voltage
324 323 TA = -40C 322 TA = 25C 321 TA = 85C 320
314 319 318 317
LT3468-2 Output Voltage
TA = 25C 316 315 TA = -40C TA = 85C
319 318 8 2 3 4 5 VIN (V) 6 7 8
3468 G14
313 312 2 3 4 5 VIN (V) 6 7 8
3468 G15
LT3468-1 Switch Current Limit
0.700
1.00
LT3468-2 Switch Current Limit
VIN = 3V VOUT = 0V 0.96
VIN = 3V VOUT = 0V
0.660
0.620
0.92
0.580
0.88
0.540
0.84
80
100
0.500 -40
-20
0 20 40 60 TEMPERATURE (C)
80
100
0.80 -40
-20
40 20 0 60 TEMPERATURE (C)
80
100
3468 G16
3468 G17
34682 G18
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LT3468/LT3468-1/LT3468-2
LT3468 curves use the circuit of Figure 6, LT3468-1 curves use the circuit of Figure 7 and LT3468-2 use the circuit of Figure 8 unless otherwise noted. LT3468 Switching Waveform
VIN = 3.6V VOUT = 100V
TYPICAL PERFOR A CE CHARACTERISTICS
VSW 10V/DIV IPRI 1A/DIV
1s/DIV
LT3468 Switching Waveform
VIN = 3.6V VOUT = 300V
VSW 10V/DIV IPRI 1A/DIV
1s/DIV
SWITCH CURRENT (mA)
UW
LT3468-1 Switching Waveform
VIN = 3.6V VOUT = 100V
LT3468-2 Switching Waveform
VIN = 3.6V VOUT = 100V
VSW 10V/DIV
VSW 10V/DIV
IPRI 1A/DIV 1s/DIV
IPRI 1A/DIV 1s/DIV
3468 G19
3468 G22
3468 G21
LT3468-1 Switching Waveform
VIN = 3.6V VOUT = 300V
LT3468-2 Switching Waveform
VIN = 3.6V VOUT = 300V
VSW 10V/DIV
VSW 10V/DIV
IPRI 1A/DIV 1s/DIV
IPRI 1A/DIV 1s/DIV
3468 G23
3468 G24
3468 G20
LT3468/LT3468-1/LT3468-2 Switch Breakdown Voltage
10 SW PIN IS RESISTIVE UNTIL BREAKDOWN 9 VOLTAGE DUE TO INTEGRATED RESISTORS. THIS DOES NOT INCREASE 8 QUIESCENT CURRENT OF PART 7 6 5 4 3 2 1 0 0 VIN = VCHARGE = 5V 10 20 30 40 50 60 70 80 90 100 SWITCH VOLTAGE (V)
3468 G25
T = 25C
T = -40C
T = 85C
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LT3468/LT3468-1/LT3468-2
PI FU CTIO S
SW (Pin 1): Switch Pin. This is the collector of the internal NPN Power switch. Minimize the metal trace area connected to this pin to minimize EMI. Tie one side of the primary of the transformer to this pin. The target output voltage is set by the turns ratio of the transformer. Choose Turns Ratio N by the following equation: N= VOUT + 2 31.5 DONE (Pin 3): Open NPN Collector Indication Pin. When target output voltage is reached, NPN turns on. This pin needs a pull-up resistor or current source. CHARGE (Pin 4): Charge Pin. This pin must be brought high (>1V) to enable the part. A low (<0.3V) to high (>1V) transition on this pin puts the part into power delivery mode. Once the target output voltage is reached, the part will stop charging the output. Toggle this pin to start charging again. Ground to shut down. You may bring this pin low during a charge cycle to halt charging at any time. VIN (Pin 5): Input Supply Pin. Must be locally bypassed with a good quality ceramic capacitor. Input supply must be 2.5V or higher.
Where: VOUT is the desired output voltage.
You must tie a Schottky diode from GND to SW, with the anode at GND for proper operation of the circuit. Please refer to the applications section for further information.
GND (Pin 2): Ground. Tie directly to local ground plane.
BLOCK DIAGRA
TO BATTERY C1 PRIMARY
3
DONE
Q3
Q1 ENABLE MASTER LATCH Q S Q R A2 R1 2.5k R DRIVER S Q Q1
CHARGE
4
ONESHOT CHIP ENABLE
LT3468: RSENSE = 0.015 LT3468-2: RSENSE = 0.022 LT3468-1: RSENSE = 0.03
6
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T1
D1 VOUT SECONDARY
D2
5
VIN R2 60k DCM COMPARATOR
1
SW
+
COUT PHOTOFLASH CAPACITOR
+
ONESHOT A3
-
Q2
+ -
36mV
+ -
VOUT COMPARATOR 1.25V REFERENCE A1
+
20mV RSENSE GND
-
+-
2
3486 BD
Figure 1
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LT3468/LT3468-1/LT3468-2
OPERATIO
The LT3468/LT3468-1/LT3468-2 are designed to charge photoflash capacitors quickly and efficiently. The operation of the part can be best understood by referring to Figure 1. When the CHARGE pin is first driven high, a one shot sets both SR latches in the correct state. The power NPN device, Q1, turns on and current begins ramping up in the primary of transformer T1. Comparator A1 monitors the switch current and when the peak current reaches 1.4A (LT3468), 1A(LT3468-2) or 0.7A (LT3468-1), Q1 is turned off. Since T1 is utilized as a flyback transformer, the flyback pulse on the SW pin will cause the output of A3 to be high. The voltage on the SW pin needs to be at least 36mV higher than VIN for this to happen. During this phase, current is delivered to the photoflash capacitor via the secondary and diode D1. As the secondary current decreases to zero, the SW pin voltage will begin to collapse. When the SW pin voltage drops to 36mV above VIN or lower, the output of A3 (DCM Comparator) will go low. This fires a one shot which turns Q1 back on. This cycle will continue to deliver power to the output. Output voltage detection is accomplished via R2, R1, Q2, and comparator A2 (VOUT Comparator). Resistors R1 and R2 are sized so that when the SW voltage is 31.5V above VIN, the output of A2 goes high which resets the master latch. This disables Q1 and halts power delivery. NPN transistor Q3 is turned on pulling the DONE pin low,
APPLICATIO S I FOR ATIO
Choosing The Right Device (LT3468/LT3468-1/ LT3468-2) The only difference between the three versions of the LT3468 is the peak current level. For the fastest possible charge time, use the LT3468. The LT3468-1 has the lowest peak current capability, and is designed for applications that need a more limited drain on the batteries. Due to the lower peak current, the LT3468-1 can use a physically smaller transformer. The LT3468-2 has a current limit in between that of the LT3468 and the LT3468-1. Transformer Design The flyback transformer is a key element for any LT3468/ LT3468-1/LT3468-2 design. It must be designed carefully
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indicating that the part has finished charging. Power delivery can only be restarted by toggling the CHARGE pin. The CHARGE pin gives full control of the part to the user. The charging can be halted at any time by bringing the CHARGE pin low. Only when the final output voltage is reached will the DONE pin go low. Figure 2 shows these various modes in action. When CHARGE is first brought high, charging commences. When CHARGE is brought low during charging, the part goes into shutdown and VOUT no longer rises. When CHARGE is brought high again, charging resumes. When the target VOUT voltage is reached, the DONE pin goes low and charging stops. Finally the CHARGE pin is brought low again so the part enters shutdown and the DONE pin goes high.
LT3468-2 VIN = 3.6V VOUT COUT = 50F 100V/DIV VDONE 5V/DIV VCHARGE 5V/DIV 1s/DIV
3468 F02
Figure 2. Halting the Charging Cycle with the CHARGE Pin
and checked that it does not cause excessive current or voltage on any pin of the part. The main parameters that need to be designed are shown in Table 1. The first transformer parameter that needs to be set is the turns ratio N. The LT3468/LT3468-1/LT3468-2 accomplish output voltage detection by monitoring the flyback waveform on the SW pin. When the SW voltage reaches 31.5V higher than the VIN voltage, the part will halt power delivery. Thus, the choice of N sets the target output voltage as it changes the amplitude of the reflected voltage from the output to the SW pin. Choose N according to the following equation: N= VOUT + 2 31.5
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LT3468/LT3468-1/LT3468-2
APPLICATIO S I FOR ATIO
Where: VOUT is the desired output voltage. The number 2 in the numerator is used to include the effect of the voltage drop across the output diode(s). Thus for a 320V output, N should be 322/31.5 or 10.2. For a 300V output, choose N equal to 302/31.5 or 9.6. The next parameter that needs to be set is the primary inductance, LPRI. Choose LPRI according to the following formula:
VOUT * 200 * 10 -9 N * IPK Where: V OUT is the desired output voltage. N is the transformer turns ratio. IPK is 1.4 (LT3468), 0.7 (LT3468-1), and 1.0 (LT3468-2). LPRI
LPRI needs to be equal or larger than this value to ensure that the LT3468/LT3468-1/LT3468-2 has adequate time to respond to the flyback waveform. All other parameters need to meet or exceed the recommended limits as shown in Table 1. A particularly important parameter is the leakage inductance, LLEAK. When the power switch of the LT3468/LT3468-1/LT3468-2 turns
Table 1. Recommended Transformer Parameters
PARAMETER LPRI LLEAK N VISO ISAT RPRI RSEC NAME Primary Inductance Primary Leakage Inductance Secondary: Primary Turns Ratio Secondary to Primary Isolation Voltage Primary Saturation Current Primary Winding Resistance Secondary Winding Resistance
VIN = 5V VOUT = 320V
VSW 10V/DIV
0V
3420 F07
100ns/DIV
3468 G18
Figure 3. LT3468 SW Voltage Waveform
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off, the leakage inductance on the primary of the transformer causes a voltage spike to occur on the SW pin. The height of this spike must not exceed 40V, even though the absolute maximum rating of the SW Pin is 50V. The 50V absolute maximum rating is a DC blocking voltage specification, which assumes that the current in the power NPN is zero. Figure 3 shows the SW voltage waveform for the circuit of Figure 6(LT3468). Note that the absolute maximum rating of the SW pin is not exceeded. Make sure to check the SW voltage waveform with VOUT near the target output voltage, as this is the worst case condition for SW voltage. Figure 4 shows the various limits on the SW voltage during switch turn off. It is important not to minimize the leakage inductance to a very low level. Although this would result in a very low leakage spike on the SW pin, the parasitic capacitance of the transformer would become large. This will adversely effect the charge time of the photoflash circuit. Linear Technology has worked with several leading magnetic component manufacturers to produce pre-designed flyback transformers for use with the LT3468/LT3468-1/ LT3468-2. Table 2 shows the details of several of these transformers.
TYPICAL RANGE LT3468 >5 100 to 300 8 to 12 >500 >1.6 <300 <40 TYPICAL RANGE LT3468-1 >10 200 to 500 8 to 12 >500 >0.8 <500 <80 TYPICAL RANGE LT3468-2 >7 200 to 500 8 to 12 >500 >1.0 <400 <60 V A m UNITS H nH
"B" "A" VSW MUST BE LESS THAN 50V MUST BE LESS THAN 40V
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Figure 4. New Transformer Design Check (Not to Scale).
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LT3468/LT3468-1/LT3468-2
APPLICATIO S I FOR ATIO
FOR USE WITH LT3468/LT3468-2 LT3468-1 TRANSFORMER NAME SBL-5.6-1 SBL-5.6S-1
Table 2. Pre-Designed Transformers - Typical Specifications Unless Otherwise Noted.
SIZE (W x L x H) mm 5.6 x 8.5 x 4.0 5.6 x 8.5 x 3.0 LPRI (H) 10 24
LPRI-LEAKAGE
LT3468 LT3468-1 LT3468-2 LT3468/LT3468-1 LT3468-1
LDT565630T-001 LDT565630T-002 LDT565630T-003 T-15-089 T-15-083
5.8 x 5.8 x 3.0 5.8 x 5.8 x 3.0 5.8 x 5.8 x 3.0 6.4 x 7.7 x 4.0 8.0 x 8.9 x 2.0
Capacitor Selection For the input bypass capacitor, a high quality X5R or X7R type should be used. Make sure the voltage capability of the part is adequate. Output Diode Selection The rectifying diode(s) should be low capacitance type with sufficient reverse voltage and forward current ratings. The peak reverse voltage that the diode(s) will see is approximately: VPK -R = VOUT + (N * VIN ) The peak current of the diode is simply: IPK -SEC = IPK -SEC = 1.4 (LT3468) N 1.0 (LT3468-2) N
Table 3. Recommended Output Diodes
PART GSD2004S (Dual Diode) BAV23S (Dual Diode) MMBD3004S MAX REVERSE VOLTAGE (V) 2x300 MAX FORWARD CONTINUOUS CURRENT (mA) 225 CAPACITANCE (pF) 5 VENDOR Vishay (402) 563-6866 www.vishay.com Philips Semiconductor (800) 234-7381 www.philips.com Diodes Incorporated (805) 446-4800 www.diodes.com
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2x250
2x350
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(nH) 200 Max 400 Max N 10.2 10.2 RPRI (m) 103 305 RSEC () 26 55 VENDOR Kijima Musen Hong Kong Office 852-2489-8266 (ph) kijimahk@netvigator.com (email) TDK Chicago Sales Office (847) 803-6100 (ph) www.components.tdk.com Tokyo Coil Engineering Japan Office 0426-56-6262 (ph) www.tokyo-coil.co.jp 6 14.5 10.5 12 20 200 Max 500 Max 550 Max 400 Max 500 Max 10.4 10.2 10.2 10.2 10.2 100 Max 10 Max 240 Max 16.5 Max 210 Max 14 Max 211 Max 27 Max 675 Max 35 Max
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0.7 (LT3468-1) N For the circuit of Figure 6 with VIN of 5V, VPK-R is 371V and IPK-SEC is 137mA. The GSD2004S dual silicon diode is recommended for most LT3468/LT3468-1/LT3468-2 applications. Another option is to use the BAV23S dual silicon diodes. Diodes Incorporated makes a dual diode named MMBD3004S which also meets all the requirements. Table 3 shows the various diodes and relevant specifications. Use the appropriate number of diodes to achieve the necessary reverse breakdown voltage. IPK -SEC = SW Pin Clamp Diode Selection The diode D2 in Figure 6 is needed to clamp the SW node. Due to the new control scheme of the LT3468/LT3468-1/ LT3468-2, the SW node may go below ground during a switch cycle. The clamp diode prevents the SW node from going too far below ground. The diode is required for proper operation of the circuit. The recommended diode
225
5
225
5
9
LT3468/LT3468-1/LT3468-2
APPLICATIO S I FOR ATIO U
Keep the area for the high voltage end of the secondary as small as possible. Also note the larger than minimum spacing for all high voltage nodes in order to meet breakdown voltage requirements for the circuit board. It is imperative to keep the electrical path formed by C1, the primary of T1, and the LT3468/LT3468-1/LT3468-2 as short as possible. If this path is haphazardly made long, it will effectively increase the leakage inductance of T1, which may result in an overvoltage condition on the SW pin.
VIN R1 DONE
SECONDARY
should be a Schottky diode with at least a 500mA peak forward current capability. The diode forward voltage drop should be 600mV or less at 500mA of forward current. Reverse voltage rating should be 40V or higher. Table 4 shows various recommended clamping diodes.
Table 4. Recommended Clamp Diodes
PART ZHCS400 MAX REVERSE VOLTAGE (V) 40 VENDOR Zetex (631) 360-2222 www.zetex.com Diodes Inc. (805) 446-4800 www.diodes.com Panasonic (408) 487-9510 www.panasonic.co.jp
B0540W
40
PRIMARY
MA2Z720
40
2 5 1 D2
Board Layout
3468 F05
The high voltage operation of the LT3468/LT3468-1/ LT3468-2 demands careful attention to board layout. You will not get advertised performance with careless layout. Figure 5 shows the recommended component placement.
Figure 5. Suggested Layout: Keep Electrical Path Formed by C1, Transformer Primary and LT3468/LT3468-1/LT3468-2 Short
TYPICAL APPLICATIO S
VIN 2.5V TO 8V T1 1:10.2 C1 4.7F 1 2 4 5 D1 320V
VIN 2.5V TO 8V
T1 1:10.2 C1 4.7F 4 3 5 6
+
R1 100k DONE CHARGE VIN LT3468 DONE CHARGE GND SW D2
COUT PHOTOFLASH CAPACITOR
R1 100k DONE CHARGE
VIN
SW
LT3468-1 GND DONE CHARGE
3468 F06
C1: 4.7F, X5R OR X7R, 10V T1: KIJIMA MUSEN PART# SBL-5.6-1, LPRI = 10H, N = 10.2 D1: VISHAY GSD2004S DUAL DIODE CONNECTED IN SERIES D2: ZETEX ZHCS400 OR EQUIVALENT R1: PULL UP RESISTOR NEEDED IF DONE PIN USED
C1: 4.7F, X5R OR X7R, 10V T1: KIJIMA MUSEN PART# SBL-5.6S-1, LPRI = 24H, N = 10.2 D1: VISHAY GSD2004S DUAL DIODE CONNECTED IN SERIES D2: ZETEX ZHCS400 OR EQUIVALENT R1: PULL UP RESISTOR NEEDED IF DONE PIN USED
Figure 6. LT3468 Photoflash Charger Uses High Efficiency 4mm Tall Transformer
Figure 7. LT3468-1 Photoflash Charger Uses High Efficiency 3mm Tall Transformer
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C1
D1 (DUAL DIODE)
CHARGE 4 3 T1
*
COUT PHOTOFLASH CAPACITOR
+
D1 320V
+
D2
COUT PHOTOFLASH CAPACITOR
3468 F07
LT3468/LT3468-1/LT3468-2
TYPICAL APPLICATIO S
VIN 2.5V TO 8V T1 1:10.2 C1 4.7F 5 8 4 1 D1 320V
C1: 4.7F, X5R OR X7R, 10V T1: TDK LDT565630T-003 LPRI = 10.5H, N = 10.2 D1: VISHAY GSD2004S DUAL DIODE CONNECTED IN SERIES D2: ZETEX ZHCS400 OR EQUIVALENT R1: PULL UP RESISTOR NEEDED IF DONE PIN USED
Figure 8. LT3468-2 Photoflash Charger Uses High Efficiency 3mm Tall Transformer
PACKAGE DESCRIPTIO
0.62 MAX
0.95 REF
3.85 MAX 2.62 REF
RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR
0.20 BSC 1.00 MAX DATUM `A'
0.30 - 0.50 REF 0.09 - 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
U
+
R1 100k DONE CHARGE VIN SW D2
COUT PHOTOFLASH CAPACITOR
LT3468-2 GND DONE CHARGE
3468 F08
S5 Package 5-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1635)
2.90 BSC (NOTE 4)
1.22 REF
1.4 MIN
2.80 BSC
1.50 - 1.75 (NOTE 4)
PIN ONE 0.30 - 0.45 TYP 5 PLCS (NOTE 3)
0.95 BSC
0.80 - 0.90 0.01 - 0.10
1.90 BSC
S5 TSOT-23 0302
346812fa
11
LT3468/LT3468-1/LT3468-2
TYPICAL APPLICATIO S
LT3468 Photoflash Circuit uses Tiny 3mm Tall Transformer
T1 1:10.4 C1 4.7F 5, 6 7, 8 5 R1 100k DONE CHARGE 3 4 VIN LT3468 DONE CHARGE GND 1 SW 2 D2 4 1 D1 320V
10 9 8
VIN 2.5V TO 8V
CHARGE TIME (s)
C1: 4.7F, X5R OR X7R, 10V T1: TDK PART# LDT565630T-001, LPRI = 6H, N = 10.4 D1: VISHAY GSD2004S DUAL DIODE CONNECTED IN SERIES D2: ZETEX ZHCS400 OR EQUIVALENT R1: PULL UP RESISTOR NEEDED IF DONE PIN USED
LT3468-1 Photoflash Circuit uses Tiny 3mm Tall Transformer
T1 1:10.2 C1 4.7F 5 8 5 R1 100k DONE CHARGE 3 4 VIN 1 SW D2 4 1 D1 320V
10 9
VIN 2.5V TO 8V
CHARGE TIME (s)
LT3468-1 2 GND DONE CHARGE
C1: 4.7F, X5R OR X7R, 10V T1: TDK PART# LDT565630T-002, LPRI = 14.5H, N = 10.2 D1: VISHAY GSD2004S DUAL DIODE CONNECTED IN SERIES D2: ZETEX ZHCS400 OR EQUIVALENT R1: PULL UP RESISTOR NEEDED IF DONE PIN USED
RELATED PARTS
PART NUMBER LTC3407 LT3420/LT3420-1 LTC3425 LTC3440/LTC3441 DESCRIPTION Dual 600mA (IOUT), 1.5MHz, Synchronous Step-Down DC/DC Converter 1.4A/1A, Photoflash Capacitor Chargers with Automatic Top-Off 5A ISW, 8MHz, Multi-Phase Synchronous Step-Up DC/DC Converter COMMENTS 96% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN): 0.6V, IQ: 40A, ISD: <1A, MS10E Charges 220F to 320V in 3.7 seconds from 5V, VIN: 2.2V to 16V, IQ: 90A, ISD: <1A, MS10 95% Efficiency, VIN: 0.5V to 4.5V, VOUT(MIN): 5.25V, IQ: 12A, ISD: <1A, QFN-32
600mA/1A (IOUT), Synchronous Buck-Boost DC/DC Converter 95% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN): 2.5V to 5.5V, IQ: 25A, ISD: <1A, MS-10, DFN-12
346812fa
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
U
Charge Time
+
COUT PHOTOFLASH CAPACITOR
7 6 5 4 3 2 1 0 2 3 4 COUT = 50F COUT = 100F
3468 TA03
5 6 VIN (V)
7
8
9
3468 TA05
Charge Time
+
8
COUT PHOTOFLASH CAPACITOR
7 6 5 4 3 2 1 0 2 COUT = 20F 3 4 5 6 VIN (V) 7 8 9 COUT = 50F
3468 TA04
3468 TA06
LT/TP 0105 1K REV A * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2003

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