LINER LT3468-2 Photoflash capacitor chargers in thinsot Datasheet

LT3468/LT3468-1/LT3468-2
Photoflash Capacitor
Chargers in ThinSOT TM
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FEATURES
DESCRIPTIO
■
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.
■
■
■
■
■
■
■
■
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, VIN = 3.6V)
5.7s for LT3468-2 (0V to 320V, 100µF, VIN = 3.6V)
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
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation. *U.S. Patent # 6, 518, 733
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■
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.
TYPICAL APPLICATIO
LT3468 Photoflash Charger Uses
High Efficiency 4mm Tall Transformer
LT3468 Charging Waveform
DANGER HIGH VOLTAGE – OPERATION BY HIGH VOLTAGE
TRAINED PERSONNEL ONLY
VIN = 3.6V
COUT = 100µF
1:10.2
VIN
2.5V TO 8V
1
4
2
5
320V
4.7µF
+
100µF
100k
SW
VIN
AVERAGE
INPUT
CURRENT
1A/DIV
LT3468
DONE
CHARGE
DONE
VOUT
50V/DIV
GND
1s/DIV
3468 G01
CHARGE
346812 TA01
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LT3468/LT3468-1/LT3468-2
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ABSOLUTE
AXI U RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
ORDER PART
NUMBER
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
TOP VIEW
SW 1
LT3468ES5
LT3468ES5-1
LT3468ES5-2
5 VIN
GND 2
DONE 3
4 CHARGE
S5 PART
MARKING
S5 PACKAGE
5-LEAD PLASTIC TSOT-23
TJMAX = 125°C
θJA = 150°C ON BOARD OVER
GROUND PLANE
θJC = 90°C/W
LTAEC
LTAGQ
LTBCH
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● 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 the LT3468, LT3468-1 and LT3468-2 unless otherwise noted.
PARAMETER
CONDITIONS
Quiescent Current
Not Switching
VCHARGE = 0V
MIN
●
Input Voltage Range
Switch Current Limit
LT3468 (Note 3)
LT3468-2
LT3468-1
Switch VCESAT
LT3468, ISW = 1A
LT3468-2, ISW = 650mA
LT3468-1, ISW = 400mA
VOUT Comparator Trip Voltage
Measured as VSW – VIN
VOUT Comparator Overdrive
300ns Pulse Width
DCM Comparator Trip Voltage
Measured as VSW – VIN
CHARGE Pin Current
VCHARGE = 3V
VCHARGE = 0V
Switch Leakage Current
VIN = VSW = 5V, in Shutdown
MAX
5
0
8
1
mA
µA
16
V
1.2
0.87
0.55
1.3
0.97
0.65
A
A
A
330
210
150
430
280
200
mV
mV
mV
31.5
32
V
200
400
mV
36
80
mV
15
0
40
0.1
µA
µA
0.01
1
µA
2.5
1.1
0.77
0.45
●
31
●
10
●
●
CHARGE Input Voltage High
TYP
1
V
●
CHARGE Input Voltage Low
UNITS
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
VDONE = 3V, DONE NPN Off
20
100
nA
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.
sn346812 346812fs
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LT3468/LT3468-1/LT3468-2
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TYPICAL PERFOR A CE CHARACTERISTICS
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
LT3468-1 Charging Waveform
VIN = 3.6V
COUT = 100µF
VIN = 3.6V
COUT = 50µF
LT3468-2 Charging Waveform
VIN = 3.6V
COUT = 100µF
VOUT
50V/DIV
VOUT
50V/DIV
VOUT
50V/DIV
AVERAGE
INPUT
CURRENT
1A/DIV
AVERAGE
INPUT
CURRENT
0.5A/DIV
1s/DIV
3468 G01
10
TA = 25°C
LT3468-2 Charge Time
TA = 25°C
9
8
8
8
7
7
7
5
COUT = 100µF
4
3
2
CHARGE TIME (s)
9
6
6
5
COUT = 50µF
4
3
2
COUT = 50µF
1
0
3
4
5
6
VIN (V)
7
8
9
3
4
5
6
VIN (V)
7
8
VIN = 2.8V
VIN = 4.2V
VIN = 3.6V
200
0
100
150 200
VOUT (V)
250
300
3468 G07
3
6
5
VIN (V)
4
7
LT3468-2 Input Current
TA = 25°C
300
VIN = 2.8V
200
VIN = 4.2V
VIN = 3.6V
100
9
8
3468 G06
600
0
50
COUT = 50µF
2
9
AVERAGE INPUT CURRENT (mA)
AVERAGE INPUT CURRENT (mA)
AVERAGE INPUT CURRENT (mA)
TA = 25°C
0
3
LT3468-1 Input Current
400
600
COUT = 100µF
4
3468 G05
LT3468 Input Current
400
5
0
2
3468 G04
800
6
1
0
2
TA = 25°C
2
COUT = 20µF
1
3468 G03
1s/DIV
10
9
CHARGE TIME (s)
CHARGE TIME (s)
3468 G02
LT3468-1 Charge Time
LT3468 Charge Time
10
1s/DIV
AVERAGE
INPUT
CURRENT
0.5A/DIV
TA = 25°C
450
VIN = 2.8V
300
VIN = 4.2V
VIN = 3.6V
150
0
0
50
100
150 200
VOUT (V)
250
300
3468 G08
0
50
100
150 200
VOUT (V)
250
300
3468 G09
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LT3468/LT3468-1/LT3468-2
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TYPICAL PERFOR A CE CHARACTERISTICS
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 = 25°C
90
TA = 25°C
80
80
EFFICIENCY (%)
VIN = 2.8V
VIN = 3.6V
60
50
VIN = 2.8V
70
EFFICIENCY (%)
80
70
VIN = 3.6V
60
50
40
100
150
200
VOUT (V)
250
300
LT3468 Output Voltage
60
100
150
200
VOUT (V)
250
TA = –40°C
319
323
318
TA = 25°C
TA = 25°C
321
TA = 85°C
TA = 85°C
316
315
320
TA = –40°C
314
319
319
318
313
318
3
4
5
VIN (V)
6
7
8
312
2
3
4
5
VIN (V)
6
3468 G13
8
2
0.700
4
5
VIN (V)
6
ILIM (A)
7
8
LT3468-2 Switch Current Limit
1.00
VIN = 3V
VOUT = 0V
VIN = 3V
VOUT = 0V
0.660
0.96
0.620
0.92
ILIM (A)
VIN = 3V
VOUT = 0V
1.3
3
3468 G15
LT3468-1 Switch Current Limit
1.4
ILIM (A)
7
3468 G14
LT3468 Switch Current Limit
1.5
300
317
VOUT (V)
VOUT (V)
320
2
250
LT3468-2 Output Voltage
324
TA = –40°C
TA = 85°C
200
150
VOUT (V)
3468 G12
322
TA = 25°C
100
50
300
LT3468-1 Output Voltage
322
VOUT (V)
VIN = 3.6V
3468 G11
324
321
VIN = 2.8V
70
40
50
3468 G10
323
VIN = 4.2V
50
40
50
TA = 25°C
VIN = 4.2V
VIN = 4.2V
EFFICIENCY (%)
LT3468-2 Efficiency
LT3468-1 Efficiency
90
0.580
0.88
0.540
0.84
1.2
1.1
–40
–20
0
20
40
60
TEMPERATURE (°C)
80
100
3468 G16
0.500
–40
–20
0
20
40
60
TEMPERATURE (°C)
80
100
3468 G17
0.80
–40
–20
40
20
0
60
TEMPERATURE (°C)
80
100
34682 G18
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LT3468/LT3468-1/LT3468-2
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TYPICAL PERFOR A CE CHARACTERISTICS
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
LT3468-2 Switching Waveform
LT3468-1 Switching Waveform
VIN = 3.6V
VOUT = 100V
VIN = 3.6V
VOUT = 100V
VIN = 3.6V
VOUT = 100V
VSW
10V/DIV
IPRI
1A/DIV
1µs/DIV
VSW
10V/DIV
VSW
10V/DIV
IPRI
1A/DIV
IPRI
1A/DIV
1µs/DIV
3468 G19
VIN = 3.6V
VOUT = 300V
VIN = 3.6V
VOUT = 300V
VIN = 3.6V
VOUT = 300V
VSW
10V/DIV
IPRI
1A/DIV
VSW
10V/DIV
VSW
10V/DIV
IPRI
1A/DIV
IPRI
1A/DIV
1µs/DIV
1µs/DIV
3468 G20
3468 G21
LT3468-2 Switching Waveform
LT3468-1 Switching Waveform
LT3468 Switching Waveform
3468 G24
3468 G23
LT3468/LT3468-1/LT3468-2
Switch Breakdown Voltage
10
SWITCH CURRENT (mA)
1µs/DIV
1µs/DIV
3468 G22
SW PIN IS RESISTIVE UNTIL BREAKDOWN
9 VOLTAGE DUE TO INTEGRATED
RESISTORS. THIS DOES NOT INCREASE
8 QUIESCENT CURRENT OF PART
7
T = 25°C
6
5
4
T = –40°C
T = 85°C
3
2
1
VIN = VCHARGE = 5V
0
0
10 20 30 40 50 60 70 80 90 100
SWITCH VOLTAGE (V)
3468 G25
sn346812 346812fs
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LT3468/LT3468-1/LT3468-2
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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
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.
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.
GND (Pin 2): Ground. Tie directly to local ground plane.
W
BLOCK DIAGRA
D1
T1
TO BATTERY
VOUT
PRIMARY
C1
SECONDARY
D2
3
DONE
5
VIN
+
SW
1
R2
60k
Q3
COUT
PHOTOFLASH
CAPACITOR
DCM COMPARATOR
+
ONESHOT
A3
–
+
–
36mV
Q2
Q1
ENABLE
MASTER
LATCH
Q
S
R1
2.5k
Q
R
DRIVER
R
S
Q1
Q
+
A2
–
+
1.25V
REFERENCE
A1
VOUT COMPARATOR
CHARGE
4
20mV
–
ONESHOT
RSENSE
+–
2
GND
CHIP ENABLE
LT3468: RSENSE = 0.015Ω
LT3468-2: RSENSE = 0.022Ω
LT3468-1: RSENSE = 0.03Ω
3486 BD
Figure 1
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LT3468/LT3468-1/LT3468-2
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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,
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 = 50µF
100V/DIV
VDONE
5V/DIV
VCHARGE
5V/DIV
1s/DIV
3468 F02
Figure 2. Halting the Charging Cycle with the CHARGE Pin.
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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
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
sn346812 346812fs
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LT3468/LT3468-1/LT3468-2
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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
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.
Table 1. Recommended Transformer Parameters
TYPICAL RANGE
LT3468
PARAMETER
NAME
LPRI
Primary Inductance
LLEAK
Primary Leakage Inductance
N
Secondary: Primary Turns Ratio
VISO
ISAT
TYPICAL RANGE
LT3468-1
TYPICAL RANGE
LT3468-2
UNITS
>5
>10
>7
µH
100 to 300
200 to 500
200 to 500
nH
8 to 12
8 to 12
8 to 12
Secondary to Primary Isolation Voltage
>500
>500
>500
V
Primary Saturation Current
>1.6
>0.8
>1.0
A
RPRI
Primary Winding Resistance
<300
<500
<400
mΩ
RSEC
Secondary Winding Resistance
<40
<80
<60
Ω
VIN = 5V
VOUT = 320V
“B”
“A”
VSW
MUST BE
LESS THAN 50V
MUST BE
LESS THAN 40V
VSW
10V/DIV
0V
3420 F07
100ns/DIV
3468 G18
Figure 3. LT3468 SW Voltage Waveform
Figure 4. New Transformer Design Check (Not to Scale).
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LT3468/LT3468-1/LT3468-2
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APPLICATIO S I FOR ATIO
Table 2. Pre-Designed Transformers - Typical Specifications Unless Otherwise Noted.
FOR USE WITH
LT3468/LT3468-2
LT3468-1
LT3468
LT3468-1
LT3468-2
SIZE
(W × L × H) mm
LPRI
(µH)
LPRI-LEAKAGE
TRANSFORMER NAME
(nH)
N
RPRI
(mΩ)
RSEC
(Ω)
SBL-5.6-1
SBL-5.6S-1
5.6 × 8.5 × 4.0
5.6 × 8.5 × 3.0
10
24
200 Max
400 Max
10.2
10.2
103
305
26
55
LDT565630T-001
LDT565630T-002
LDT565630T-003
5.8 × 5.8 × 3.0
5.8 × 5.8 × 3.0
5.8 × 5.8 × 3.0
6
14.5
10.5
200 Max
500 Max
550 Max
10.4
10.2
10.2
100 Max 10 Max
240 Max 16.5 Max
210 Max 14 Max
TDK
Chicago Sales Office
(847) 803-6100 (ph)
www.components.tdk.com
T-15-089
T-15-083
6.4 × 7.7 × 4.0
8.0 × 8.9 × 2.0
12
20
400 Max
500 Max
10.2
10.2
211 Max 27 Max
675 Max 35 Max
Tokyo Coil Engineering
Japan Office
0426-56-6262 (ph)
www.tokyo-coil.co.jp
LT3468/LT3468-1
LT3468-1
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:
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. Toshiba makes a dual diode named 1SS306
which also meets all the requirements. The CRF02 is a
single diode with an 800V reverse voltage rating which is
also suitable. 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
1.4
IPK −SEC =
(LT3468)
N
IPK −SEC =
VENDOR
Kijima Musen
Hong Kong Office
852-2489-8266 (ph)
[email protected] (email)
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
1.0
(LT3468-2)
N
Table 3. Recommended Output Diodes
MAX REVERSE VOLTAGE
(V)
MAX FORWARD CONTINUOUS CURRENT
(mA)
CAPACITANCE
(pF)
GSD2004S
(Dual Diode)
2x300
225
5
Vishay
(402) 563-6866
www.vishay.com
BAV23S
(Dual Diode)
2x250
225
5
Philips Semiconductor
(800) 234-7381
www.philips.com
1SS306
(Dual Diode)
CRF02
2x250
100
3
1x800
500
Not Specified
Toshiba
(949) 455-2000
www.semicon.toshiba.co.jp
PART
VENDOR
sn346812 346812fs
9
LT3468/LT3468-1/LT3468-2
U
U
W
U
APPLICATIO S I FOR ATIO
MAX REVERSE VOLTAGE
(V)
PART
ZHCS400
VENDOR
40
B0540W
Zetex
(631) 360-2222
www.zetex.com
40
MA2Z720
Diodes Inc.
(805) 446-4800
www.diodes.com
40
VIN
C1
R1
D1
(DUAL DIODE)
DONE
CHARGE
4
3
•
2
Panasonic
(408) 487-9510
www.panasonic.co.jp
5
T1
SECONDARY
Table 4. Recommended Clamp Diodes
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.
PRIMARY
going too far below ground. The diode is required for
proper operation of the circuit. The recommended diode
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.
•
COUT
PHOTOFLASH
CAPACITOR
+
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.
U
TYPICAL APPLICATIO S
T1
1:10.2
VIN
2.5V TO 8V
C1
4.7µF
D1
1
4
2
5
320V
+
R1
100k
DONE
CHARGE
SW
VIN
COUT
PHOTOFLASH
CAPACITOR
D2
LT3468
DONE
T1
1:10.2
VIN
2.5V TO 8V
C1
4.7µF
R1
100k
CHARGE
CHARGE
4
5
3
6
320V
+
DONE
GND
D1
VIN
SW
COUT
PHOTOFLASH
CAPACITOR
D2
LT3468-1
GND
DONE
CHARGE
3468 F06
C1: 4.7µF, X5R OR X7R, 10V
T1: KIJIMA MUSEN PART# SBL-5.6-1, LPRI = 10µH, 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
C1: 4.7µF, X5R OR X7R, 10V
T1: KIJIMA MUSEN PART# SBL-5.6S-1, LPRI = 24µH, 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 F07
Figure 7. LT3468-1 Photoflash Charger Uses
High Efficiency 3mm Tall Transformer
sn346812 346812fs
10
LT3468/LT3468-1/LT3468-2
U
TYPICAL APPLICATIO S
T1
1:10.2
VIN
2.5V TO 8V
C1
4.7µF
D1
5
4
8
1
320V
+
SW
VIN
R1
100k
COUT
PHOTOFLASH
CAPACITOR
D2
LT3468-2
GND
DONE
DONE
CHARGE
CHARGE
C1: 4.7µF, X5R OR X7R, 10V
T1: TDK LDT565630T-003 LPRI = 10.5µH, 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 F08
Figure 8. LT3468-2 Photoflash Charger Uses
High Efficiency 3mm Tall Transformer
U
PACKAGE DESCRIPTIO
S5 Package
5-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1635)
0.62
MAX
0.95
REF
2.90 BSC
(NOTE 4)
1.22 REF
1.4 MIN
3.85 MAX 2.62 REF
2.80 BSC
1.50 – 1.75
(NOTE 4)
PIN ONE
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.30 – 0.45 TYP
5 PLCS (NOTE 3)
0.95 BSC
0.80 – 0.90
0.20 BSC
0.01 – 0.10
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
1.90 BSC
S5 TSOT-23 0302
sn346812 346812fs
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.
11
LT3468/LT3468-1/LT3468-2
U
TYPICAL APPLICATIO S
LT3468 Photoflash Circuit uses Tiny 3mm Tall Transformer
T1
1:10.4
C1
4.7µF
Charge Time
D1
5, 6
4
7, 8
1
9
8
+
R1
100k
3
DONE
4
CHARGE
5
1
VIN
SW
COUT
PHOTOFLASH
CAPACITOR
D2
LT3468
2
GND
DONE
10
320V
CHARGE TIME (s)
VIN
2.5V TO 8V
CHARGE
7
6
5
4
COUT = 100µF
3
2
COUT = 50µF
1
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
0
2
3
4
5
6
VIN (V)
3468 TA03
7
8
9
3468 TA05
LT3468-1 Photoflash Circuit uses Tiny 3mm Tall Transformer
T1
1:10.2
C1
4.7µF
Charge Time
D1
5
4
8
1
9
+
R1
100k
DONE
CHARGE
3
4
10
320V
5
1
VIN
SW
8
COUT
PHOTOFLASH
CAPACITOR
D2
LT3468-1
2
GND
DONE
CHARGE
CHARGE TIME (s)
VIN
2.5V TO 8V
7
6
5
4
COUT = 50µF
3
2
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
1
COUT = 20µF
0
2
3468 TA04
3
4
5
6
VIN (V)
7
8
9
3468 TA06
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PART NUMBER
DESCRIPTION
COMMENTS
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LT3420/LT3420-1
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Charges 220µF to 320V in 3.7 seconds from 5V,
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LTC3425
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95% Efficiency, VIN: 0.5V to 4.5V, VOUT(MIN): 5.25V, IQ: 12µA,
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LTC3440/LTC3441
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IQ: 25µA, ISD: <1µA, MS-10, DFN-12
sn346812 346812fs
12
Linear Technology Corporation
LT/TP 0304 1K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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