LT3468/LT3468-1/LT3468-2
Photoflash Capacitor
Chargers in ThinSOT
TM
FEATURES
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DESCRIPTIO
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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
IN
= 3.6V)
5.7s for LT3468-2 (0V to 320V, 100µF, V
IN
= 3.6V)
5.5s for LT3468-1 (0V to 320V, 50µF, V
IN
= 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
®
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
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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
4.7µF
2
5
1:10.2
1
4
320V
V
IN
= 3.6V
C
OUT
= 100µF
+
100µF
100k
DONE
CHARGE
V
IN
LT3468
DONE
CHARGE
346812 TA01
V
OUT
50V/DIV
AVERAGE
INPUT
CURRENT
1A/DIV
SW
GND
U
LT3468 Charging Waveform
1s/DIV
3468 G01
U
U
346812fa
1
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
V
IN
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
LT3468ES5
LT3468ES5-1
LT3468ES5-2
S5 PART
MARKING
LTAEC
LTAGQ
LTBCH
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
T
JMAX
= 125°C
θ
JA
= 150°C ON BOARD OVER
GROUND PLANE
θ
JC
= 90°C/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 T
A
= 25°C. V
IN
= 3V, V
CHARGE
= V
IN
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, I
SW
= 1A
LT3468-2, I
SW
= 650mA
LT3468-1, I
SW
= 400mA
Measured as V
SW
– V
IN
300ns Pulse Width
Measured as V
SW
– V
IN
V
CHARGE
= 3V
V
CHARGE
= 0V
V
IN
= V
SW
= 5V, in Shutdown
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
Not Switching
V
CHARGE
= 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
µA
V
A
A
A
mV
mV
mV
V
mV
mV
µA
µA
µA
V
V
µs
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 V
CESAT
V
OUT
Comparator Trip Voltage
V
OUT
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
High→Low→High
100kΩ from V
IN
to DONE
33µA into DONE Pin
V
DONE
= 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 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.
346812fa
2
U
mV
nA
W
U
U
W W
W
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
V
IN
= 3.6V
C
OUT
= 100µF
TYPICAL PERFOR A CE CHARACTERISTICS
V
OUT
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
V
IN
(V)
7
8
9
3468 G04
T
A
= 25°C
CHARGE TIME (s)
C
OUT
= 100µF
C
OUT
= 50µF
LT3468 Input Current
800
T
A
= 25°C
400
AVERAGE INPUT CURRENT (mA)
AVERAGE INPUT CURRENT (mA)
600
V
IN
= 2.8V
400
V
IN
= 4.2V
V
IN
= 3.6V
200
300
V
IN
= 2.8V
200
V
IN
= 4.2V
V
IN
= 3.6V
AVERAGE INPUT CURRENT (mA)
0
0
50
100
150 200
V
OUT
(V)
250
300
3468 G07
U W
3468 G01
LT3468-1 Charging Waveform
V
IN
= 3.6V
C
OUT
= 50µF
LT3468-2 Charging Waveform
V
IN
= 3.6V
C
OUT
= 100µF
V
OUT
50V/DIV
V
OUT
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
V
IN
(V)
7
8
9
3468 G05
LT3468-2 Charge Time
10
9
8
7
6
5
4
3
2
C
OUT
= 50µF
C
OUT
= 100µF
T
A
= 25°C
T
A
= 25°C
C
OUT
= 50µF
C
OUT
= 20µF
1
0
2
3
4
6
5
V
IN
(V)
7
8
9
3468 G06
LT3468-1 Input Current
T
A
= 25°C
600
LT3468-2 Input Current
T
A
= 25°C
450
V
IN
= 2.8V
300
V
IN
= 3.6V
V
IN
= 4.2V
100
150
0
0
50
100
150 200
V
OUT
(V)
250
300
3468 G08
0
0
50
100
150 200
V
OUT
(V)
250
300
3468 G09
346812fa
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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
T
A
= 25°C
V
IN
= 4.2V
80
EFFICIENCY (%)
TYPICAL PERFOR A CE CHARACTERISTICS
LT3468-1 Efficiency
90
T
A
= 25°C
V
IN
= 4.2V
80
70
EFFICIENCY (%)
V
IN
= 3.6V
70
EFFICIENCY (%)
V
IN
= 2.8V
60
50
40
50
100
150
200
V
OUT
(V)
250
300
3468 G10
LT3468 Output Voltage
324
323
322
V
OUT
(V)
V
OUT
(V)
T
A
= –40°C
V
OUT
(V)
321
320
319
318
2
T
A
= 25°C
T
A
= 85°C
3
4
5
V
IN
(V)
6
LT3468 Switch Current Limit
1.5
V
IN
= 3V
V
OUT
= 0V
1.4
I
LIM
(A)
1.3
I
LIM
(A)
I
LIM
(A)
1.2
1.1
–40
–20
0
20
40
60
TEMPERATURE (°C)
4
U W
7
3468 G13
LT3468-2 Efficiency
90
T
A
= 25°C
V
IN
= 4.2V
V
IN
= 2.8V
70
V
IN
= 3.6V
80
V
IN
= 2.8V
V
IN
= 3.6V
60
60
50
50
40
50
100
150
200
V
OUT
(V)
250
300
3468 G11
40
50
100
200
150
V
OUT
(V)
250
300
3468 G12
LT3468-1 Output Voltage
324
323
T
A
= –40°C
322
T
A
= 25°C
321
T
A
= 85°C
320
314
319
318
317
LT3468-2 Output Voltage
T
A
= 25°C
316
315
T
A
= –40°C
T
A
= 85°C
319
318
8
2
3
4
5
V
IN
(V)
6
7
8
3468 G14
313
312
2
3
4
5
V
IN
(V)
6
7
8
3468 G15
LT3468-1 Switch Current Limit
0.700
1.00
LT3468-2 Switch Current Limit
V
IN
= 3V
V
OUT
= 0V
0.96
V
IN
= 3V
V
OUT
= 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
346812fa
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
V
IN
= 3.6V
V
OUT
= 100V
TYPICAL PERFOR A CE CHARACTERISTICS
V
SW
10V/DIV
I
PRI
1A/DIV
1µs/DIV
LT3468 Switching Waveform
V
IN
= 3.6V
V
OUT
= 300V
V
SW
10V/DIV
I
PRI
1A/DIV
1µs/DIV
SWITCH CURRENT (mA)
U W
LT3468-1 Switching Waveform
V
IN
= 3.6V
V
OUT
= 100V
LT3468-2 Switching Waveform
V
IN
= 3.6V
V
OUT
= 100V
V
SW
10V/DIV
V
SW
10V/DIV
I
PRI
1A/DIV
1µs/DIV
I
PRI
1A/DIV
1µs/DIV
3468 G19
3468 G22
3468 G21
LT3468-1 Switching Waveform
V
IN
= 3.6V
V
OUT
= 300V
LT3468-2 Switching Waveform
V
IN
= 3.6V
V
OUT
= 300V
V
SW
10V/DIV
V
SW
10V/DIV
I
PRI
1A/DIV
1µs/DIV
I
PRI
1A/DIV
1µs/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
V
IN
= V
CHARGE
= 5V
10 20 30 40 50 60 70 80 90 100
SWITCH VOLTAGE (V)
3468 G25
T = 25°C
T = –40°C
T = 85°C
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