LT3468-1

LT3468 LINER | Alldatasheet

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Information furnished by Linear Technology Corporation is believed to be accurate and reliable. tation that the interconnection of its circuits as described herein will not infringe on existing patent rights. current limit, the two devices are otherwise equivalent. The CHARGE pin gives full control of the part to the user. , LTC and LT are registered trademarks of Linear Technology Corporation. Figure 1. LT3468 Photoflash Charger Uses

3468 TA01

Figure 2. LT3468-1 Photoflash Charger Uses

3468 TA02

Operating Temperature Range (Note 2) ...–40°C to 85°C ORDER PART NUMBER S5 PART MARKING TJMAX = 125°C, θJA = 256°C/W LTAEC LTAGQ LT3468ES5 LT3468ES5-1 ABSOLUTE AXI U RATI GSW WW U PACKAGE/ORDER I FOR ATIOUU W (Note 1) ELECTRICAL CHARACTERISTICSThe l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3V, VCHARGE = VIN unless otherwise noted. (Note 2) Specifications are for both the LT3468 and LT3468-1 unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Quiescent Current Not Switching 5 8 mA VCHARGE = 0V 0 1 µA Input Voltage Range l 2.5 16 V Switch Current Limit LT3468 (Note 3) 1.1 1.2 1.3 A LT3468-1 0.45 0.55 0.65 A Switch VCESAT LT3468, ISW = 1A 330 430 mV LT3468-1, ISW = 400mA 150 200 mV VOUT Comparator Trip Voltage Measured as V SW – VIN l 31 31.5 32 V VOUT Comparator Overdrive 300ns Pulse Width 200 400 mV DCM Comparator Trip Voltage Measured as V SW – VIN l 10 36 80 mV CHARGE Pin Current V CHARGE = 3V 15 40 µA VCHARGE = 0V 0 0.1 µA Switch Leakage Current V IN = VSW = 5V, in Shutdown l 0.01 1 µA CHARGE Input Voltage High l 1V CHARGE Input Voltage Low l 0.3 V DONE Output Signal High 100k Ω from VIN to DONE 3 V DONE Output Signal Low 33 µA into DONE Pin 100 200 mV DONE Leakage Current V DONE = 3V, DONE NPN Off 20 100 nA Consult LTC Marketing for parts specified with wider operating temperature ranges. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT3468E/LT3468E-1 are guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C 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.

5 VIN

4 CHARGE

LT3468-1 Charging Waveform LT3468 Input Current LT3468-1 Input Current LT3468 Charging Waveform LT3468 Charge Time VIN (V) 23456789 CHARGE TIME (s)

3468 G03

COUT = 50µF COUT = 100µF TA = 25°C VIN (V) 23456789 CHARGE TIME (s)

3468 G04

COUT = 20µF COUT = 50µF TA = 25°C VOUT (V) 0 50 100 150 200 250 300 AVERAGE INPUT CURRENT (mA)

3468 G05

VIN = 2.8V VIN = 4.2V VIN = 3.6V TA = 25°C VOUT (V) 0 50 100 150 200 250 300 AVERAGE INPUT CURRENT (mA)

3468 G06

VIN = 2.8V VIN = 4.2V VIN = 3.6V TA = 25°C LT3468 Efficiency LT3468-1 Efficiency VOUT (V) 50 100 150 200 250 300 EFFICIENCY (%)

3468 G07

VIN = 2.8V VIN = 4.2V VIN = 3.6V TA = 25°C VOUT (V) 50 100 150 200 250 300 EFFICIENCY (%)

3468 G08

VIN = 2.8V VIN = 4.2V VIN = 3.6V TA = 25°C VIN = 3.6V COUT = 50µF

3468 G01 3468 G02

TYPICAL PERFOR A CE CHARACTERISTICSUW 1s/DIV VIN = 3.6V COUT = 100µF VOUT 50V/DIV 1s/DIV AVERAGE INPUT CURRENT 1A/DIV VOUT 50V/DIV AVERAGE INPUT CURRENT 0.5A/DIV LT3468 curves use the circuit of Figure 1 and LT3468-1 curves use the circuit of Figure 2 unless otherwise noted.

LT3468-1 Switch Current Limit LT3468-1 Output Voltage LT3468 Switching Waveform LT3468 Switching Waveform LT3468-1 Switching Waveform LT3468/LT3468-1 Switch Breakdown VoltageLT3468-1 Switching Waveform LT3468 Output Voltage LT3468 Switch Current Limit VIN (V) 2345678 VOUT (V)

3468 G09

TA = –40°C TA = 25°C TA = 85°C VIN (V) 2345678 VOUT (V)

3468 G10

TA = –40°C TA = 25°C TA = 85°C TEMPERATURE (°C) –40 –20 0 20 40 60 100 80 ILIM (A)

3468 G11

1.5 1.1 1.2 1.3 1.4 VIN = 3V VOUT = 0V TEMPERATURE (°C) –40 –20 0 20 40 60 100 80 ILIM (A)

3468 G12

0.700 0.500 0.540 0.580 0.620 0.660 VIN = 3V VOUT = 0V SWITCH VOLTAGE (V) 0 1 02 03 04 05 06 07 08 09 0 1 0 0 SWITCH CURRENT (mA)

3468 G17

T = –40°C T = 25°C T = 85°C SW PIN IS RESISTIVE UNTIL BREAKDOWN VOLTAGE DUE TO INTEGRATED RESISTORS. THIS DOES NOT INCREASE QUIESCENT CURRENT OF PARTVIN = VCHARGE = 5V VIN = 3.6V VOUT = 100V VIN = 3.6V VOUT = 100V TYPICAL PERFOR A CE CHARACTERISTICSUW

3468 G131µs/DIV

3468 G141µs/DIV

VIN = 3.6V VOUT = 300V VIN = 3.6V VOUT = 300V

3468 G151µs/DIV

3468 G161µs/DIV

LT3468 curves use the circuit of Figure 1 and LT3468-1 curves use the circuit of Figure 2 unless otherwise noted.

SW (Pin 1): Switch Pin. This is the collector of the internal NPN Power switch. Minimize the metal trace area con- nected 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. 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. 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. 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. V IN (Pin 5): Input Supply Pin. Must be locally bypassed with a good quality ceramic capacitor. Input supply must be 2.5V or higher. UUUPI FU CTIO S

LT3468: RSENSE = 0.015Ω LT3468-1: RSENSE = 0.03Ω 3486 BD GND 4 2 ONE- SHOT ONE- SHOT DRIVER PRIMARY SECONDARY MASTER LATCH RSENSE DCM COMPARATOR VOUT COMPARATOR 2.5k SRQ 1.25V REFERENCE Q1QQ SR The LT3468/LT3468-1 are designed to charge photoflash capacitors quickly and efficiently. The operation of the part can be best understood by referring to Figure 3. 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 cur- rent and when the peak current reaches 1.4A (LT3468) 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 V IN for this to happen. During this phase, current is delivered to the photoflash capacitor via the secondary and diode D1. As the second- ary current decreases to zero, the SW pin voltage will begin to collapse. When the SW pin voltage drops to 36mV above V IN 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. Power delivery can only be restarted by toggling the CHARGE Pin. Figure 3

designed are shown in Table 1. Table 1. Recommended Transformer Parameters 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.

Table 2. Pre-Designed Transformers - Typical Specifications Unless Otherwise Noted. is the worst case condition for SW voltage. effect the charge time of the photoflash circuit. flyback transformers for use with the LT3468/LT3468-1. Table 2 shows the details of several of these transformers. Figure 4. LT3468 SW Voltage Waveform Figure 5. LT3468-1 SW Voltage Waveform

3468 G18100ns/DIV

3468 G19100ns/DIV

Table 3. Recommended Output Diodes recommended for most LT3468/LT3468-1 applications. Another option is to use the BAV23S dual silicon diodes. The diode D2 in Figure 1 is needed to clamp the SW node. the SW node may go below ground during a switch cycle. capability. Reverse voltage rating should be 40V or higher. Table 4 shows various recommended clamping diodes. Table 4. Recommended Clamp Diodes

requirements for the circuit board. age condition on the SW pin. Figure 6. Suggested Layout: Keep electrical path formed by C1, Transformer Primary and LT3468/LT3468-1 short.

3468 F01

1.50 – 1.75 0.25 – 0.50 TYP 5 PLCS NOTE 3 DATUM ‘A’ 0.09 – 0.20 (NOTE 3) S5 SOT-23 0502 PIN ONE 2.80 – 3.10 (NOTE 4)

0.95 BSC

1.90 BSC

0.90 – 1.30 0.90 – 1.45 0.00 – 0.150.20 BSC 0.35 – 0.55 REF 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. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ) ATTENTION: ORIGINAL SOT23-5L PACKAGE. MOST SOT23-5L PRODUCTS CONVERTED TO THIN SOT23 PACKAGE, DRAWING # 05-08-1635 AFTER APPROXIMATELY APRIL 2001 SHIP DATE

3.85 MAX

0.62 MAX 0.95 REF RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 1.4 MIN2.62 REF

1.22 REF

(Reference LTC DWG # 05-08-1633) UPACKAGE DESCRIPTIO

Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 l FAX: (408) 434-0507 l www.linear.com  LINEAR TECHNOLOGY CORPORATION 2003 LT/TP 1003 1K • PRINTED IN USA RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3407 Dual 600mA (I OUT), 1.5MHz, Synchronous Step-Down DC/DC 96% Efficiency, V IN: 2.5V to 5.5V, VOUT(MIN): 0.6V, IQ: 40µA, Converter I SD: <1µA, MS10E LT3420/LT3420-1 1.4A/1A, Photoflash Capacitor Chargers with Charges 220 µF to 320V in 3.7 seconds from 5V, Automatic Top-Off V IN: 2.2V to 16V, IQ: 90µA, ISD: <1µA, MS10 LTC3425 5A I SW, 8MHz, Multi-Phase Synchronous Step-Up DC/DC 95% Efficiency, V IN: 0.5V to 4.5V, VOUT(MIN): 5.25V, IQ: 12µA, Converter I SD: <1µA, QFN-32 LTC3440/LTC3441 600mA/1A (I OUT), Synchronous Buck-Boost DC/DC Converter 95% Efficiency, V IN: 2.5V to 5.5V, VOUT(MIN): 2.5V to 5.5V, IQ: 25µA, ISD: <1µA, MS-10, DFN-12 TYPICAL APPLICATIO SU LT3468 Photoflash Circuit uses Tiny 3mm Tall Transformer LT3468-1 Photoflash Circuit uses Tiny 3mm Tall Transformer LT3468 CHARGE GND VIN SW DONE DONE CHARGE 4.7µF 100k 1:10.4 COUT PHOTOFLASH CAPACITOR VIN 2.5V TO 8V 320V 5, 6 7, 8 C1: 4.7µF, X5R OR X7R, 10V T1: TDK PART# LDT565630T-001, LPRI = 6µH, 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

3468 TA03

4.7µF 100k 1:10.2 COUT PHOTOFLASH CAPACITOR VIN 2.5V TO 8V 320V C1: 4.7µF, X5R OR X7R, 10V T1: TDK PART# LDT565630T-002, LPRI = 14.5µH, 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

3468 TA04

VIN (V) 23456789 CHARGE TIME (s)

3468 TA05

COUT = 50µF COUT = 100µF VIN (V) 23456789 CHARGE TIME (s)

3468 TA06

COUT = 20µF COUT = 50µF