LINEAR TECHNOLOGY LT3468, LT3468-1, LT3468-2 Technical data

FEATURES

LT3468/LT3468-1/LT3468-2

Photoflash Capacitor

TM

Chargers in ThinSOT

U

DESCRIPTIO

■

Highly Integrated IC Reduces Solution Size

■

Uses Small Transformers:

5.8mm × 5.8mm × 3mm

■

Fast Photoflash Charge Times:

4.6s for LT3468 (0V to 320V, 100µF, V

5.7s for LT3468-2 (0V to 320V, 100µF, V

= 3.6V)

IN

= 3.6V)

IN

5.5s for LT3468-1 (0V to 320V, 50µF, 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

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APPLICATIO S

■

Digital / Film Camera Flash

■

PDA / Cell Phone Flash

■

Emergency Strobe

The LT®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.

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TYPICAL APPLICATIO

LT3468 Photoflash Charger Uses

High Efficiency 4mm Tall Transformer

DANGER HIGH VOLTAGE – OPERATION BY HIGH VOLTAGE

TRAINED PERSONNEL ONLY

V

IN

2.5V TO 8V

100k

DONE DONE

CHARGE

4.7µF

V

IN

CHARGE

LT3468

1:10.2

1

2

SW

GND

LT3468 Charging Waveform

VIN = 3.6V

= 100µF

C

OUT

4

5

320V

+

100µF

346812 TA01

V

OUT

50V/DIV

AVERAGE

INPUT

CURRENT

1A/DIV

1s/DIV

3468 G01

346812fa

1

LT3468/LT3468-1/LT3468-2

5 VIN

4 CHARGE

SW 1

TOP VIEW

S5 PACKAGE

5-LEAD PLASTIC TSOT-23

GND 2

DONE 3

ABSOLUTE AXI U RATI GS

(Note 1)

VIN Voltage .............................................................. 16V

SW Voltage ................................................ –0.4V to 50V

CHARGE Voltage...................................................... 10V

DONE Voltage .......................................................... 10V

Current into DONE Pin .......................................... ±1mA

Maximum Junction Temperature .......................... 125°C

Operating Temperature Range (Note 2) ...–40°C to 85°C

Storage Temperature Range ..................–65°C to 150°C

Lead Temperature (Soldering, 10 sec).................. 300°C

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C. VIN = 3V, V
are for the LT3468, LT3468-1 and LT3468-2 unless otherwise noted.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Quiescent Current Not Switching 5 8 mA

Input Voltage Range ● 2.5 16 V

Switch Current Limit LT3468 (Note 3) 1.1 1.2 1.3 A

Switch V

V

OUT

V

OUT

DCM Comparator Trip Voltage Measured as V

CHARGE Pin Current V

Switch Leakage Current VIN = VSW = 5V, in Shutdown ● 0.01 1 µA

CHARGE Input Voltage High ● 1V

CHARGE Input Voltage Low ● 0.3 V

Minimum Charge Pin Low Time High→Low→High 20 µs

DONE Output Signal High 100kΩ from VIN to DONE 3 V

DONE Output Signal Low 33µA into DONE Pin 100 200 mV

DONE Leakage Current V

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 0°C to 70°C. Specifications over the

2

WW

W

U

UUW

PACKAGE/ORDER I FOR ATIO

ORDER PART

NUMBER

LT3468ES5
LT3468ES5-1
LT3468ES5-2

S5 PART

T

= 125°C

JMAX

= 150°C ON BOARD OVER

θ

JA

GROUND PLANE

θJC = 90°C/W

Consult LTC Marketing for parts specified with wider operating temperature ranges.

The ● denotes the specifications which apply over the full operating

= VIN unless otherwise noted. (Note 2) Specifications

CHARGE

V

= 0V 0 1 µA

CHARGE

LT3468-2 0.77 0.87 0.97 A
LT3468-1 0.45 0.55 0.65 A

CESAT

Comparator Trip Voltage Measured as V

Comparator Overdrive 300ns Pulse Width 200 400 mV

LT3468, I
LT3468-2, I
LT3468-1, I

CHARGE

V

CHARGE

DONE

= 1A 330 430 mV

SW

= 650mA 210 280 mV

SW

= 400mA 150 200 mV

SW

– V

SW

IN

– V

SW

IN

= 3V 15 40 µA
= 0V 0 0.1 µA

= 3V, DONE NPN Off 20 100 nA

–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.

● 31 31.5 32 V

● 10 36 80 mV

MARKING

LTAEC
LTAGQ
LTBCH

346812fa

LT3468/LT3468-1/LT3468-2

UW

TYPICAL PERFOR A CE CHARACTERISTICS

curves use the circuit of Figure 7 and LT3468-2 use the circuit of Figure 8 unless otherwise noted.

LT3468 curves use the circuit of Figure 6, LT3468-1

LT3468 Charging Waveform

VIN = 3.6V

= 100µF

C

OUT

V

OUT

50V/DIV

AVERAGE

INPUT

CURRENT

1A/DIV

1s/DIV

LT3468 Charge Time

10

TA = 25°C

9

8

7

6

5

4

CHARGE TIME (s)

3

2

C

OUT

1

0

23456789

= 50µF

C

OUT

= 100µF

VIN (V)

3468 G01

3468 G04

LT3468-1 Charging Waveform

VIN = 3.6V

= 50µF

C

OUT

V

OUT

50V/DIV

AVERAGE

INPUT

CURRENT

0.5A/DIV

1s/DIV

LT3468-1 Charge Time

10

TA = 25°C

9

8

7

6

5

4

CHARGE TIME (s)

3

2

C

1

OUT

0

23456789

= 20µF

C

OUT

VIN (V)

= 50µF

3468 G02

3468 G05

V

OUT

50V/DIV

AVERAGE

INPUT

CURRENT

0.5A/DIV

10

9

8

7

6

5

4

CHARGE TIME (s)

3

2

1

0

LT3468-2 Charging Waveform

VIN = 3.6V
C

= 100µF

OUT

1s/DIV

LT3468-2 Charge Time

TA = 25°C

C

= 100µF

OUT

C

= 50µF

OUT

6

5

2

4

3

VIN (V)

7

8

3468 G03

9

3468 G06

LT3468 Input Current LT3468-1 Input Current

800

TA = 25°C

600

400

200

AVERAGE INPUT CURRENT (mA)

0

VIN = 2.8V

VIN = 4.2V

VIN = 3.6V

0 50 100 150 200 250 300

V

(V)

OUT

3468 G07

400

TA = 25°C

300

VIN = 2.8V

200

100

AVERAGE INPUT CURRENT (mA)

0

0 50 100 150 200 250 300

VIN = 4.2V

VIN = 3.6V

LT3468-2 Input Current

600

TA = 25°C

450

VIN = 2.8V

300

150

AVERAGE INPUT CURRENT (mA)

0

V

(V)

OUT

3468 G08

0 50 100 150 200 250 300

VIN = 3.6V

V

OUT

VIN = 4.2V

(V)

3468 G09

346812fa

3

LT3468/LT3468-1/LT3468-2

TEMPERATURE (°C)

–40

I

LIM

(A)

1.00

0.96

0.92

0.88

0.84

0.80
0

40

60

34682 G18

–20

20

80

100

VIN = 3V
V

OUT

= 0V

UW

TYPICAL PERFOR A CE CHARACTERISTICS

curves use the circuit of Figure 7 and LT3468-2 use the circuit of Figure 8 unless otherwise noted.

LT3468 curves use the circuit of Figure 6, LT3468-1

LT3468 Efficiency LT3468-1 Efficiency

90

TA = 25°C

80

VIN = 2.8V

70

60

EFFICIENCY (%)

50

40

50 100 150 200 250 300

VIN = 4.2V

VIN = 3.6V

V

(V)

OUT

3468 G10

90

TA = 25°C

80

VIN = 2.8V

70

60

EFFICIENCY (%)

50

40

50 100 150 200 250 300

LT3468-1 Output VoltageLT3468 Output Voltage

(V)

OUT

V

324

323

322

321

320

319

TA = –40°C

TA = 25°C

TA = 85°C

(V)

OUT

V

324

323

322

321

320

319

TA = –40°C

TA = 25°C

TA = 85°C

VIN = 4.2V

VIN = 3.6V

V

OUT

(V)

3468 G11

LT3468-2 Efficiency

90

TA = 25°C

80

VIN = 2.8V

70

60

EFFICIENCY (%)

50

40

50

100

VIN = 3.6V

150

V

LT3468-2 Output Voltage

319

318

317

(V)

OUT

V

316

315

314

313

TA = 85°C

TA = –40°C

OUT

200

(V)

VIN = 4.2V

250

TA = 25°C

300

3468 G12

4

318

2345678

VIN (V)

LT3468 Switch Current Limit

1.5
VIN = 3V

= 0V

V

OUT

1.4

(A)

1.3

LIM

I

1.2

1.1

–40 –20 0 20 40 60 10080

TEMPERATURE (°C)

3468 G13

3468 G16

318

2345678

VIN (V)

LT3468-1 Switch Current Limit

0.700
VIN = 3V

= 0V

V

OUT

0.660

0.620

(A)

LIM

I

0.580

0.540

0.500

–40 –20 0 20 40 60 10080

TEMPERATURE (°C)

3468 G14

3468 G17

312

2

45678

3

VIN (V)

LT3468-2 Switch Current Limit

3468 G15

346812fa