LINEAR TECHNOLOGY LT3420, LT3420-1 Technical data
查询LT3420EDD供应商
Chargers with Automatic Refresh
FEATURES
■
Charges 220µF to 320V in 3.7 Seconds
from 5V (LT3420)
■
Charges 100µF to 320V in 3.5 Seconds
from 5V (LT3420-1)
■
Charges Any Size Photoflash Capacitor
■
Supports Operation from Two AA Cells or Any
Supply from 1.8V to 16V
■
Controlled Peak Switch Current: 1.4A (LT3420)
1.0A (LT3420-1)
■
Controlled Input Current: 840mA (LT3420)
450mA (LT3420-1)
■
Uses Standard Transformers
■
Efficient Flyback Operation (>75% Typical)
■
Adjustable Output
■
Automatic Refresh
■
Charge Complete Indicator
■
No High Voltage Zener Diode Required
■
No Output Voltage Divider Required
■
Small 10-Lead MSOP Package
■
Small 10-Lead (3mm × 3mm) DFN Package
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APPLICATIO S
■
Digital Camera Flash Unit
■
Film Camera Flash Unit
■
High Voltage Power Supplies
LT3420/LT3420-1
Photoflash Capacitor
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DESCRIPTIO
The LT®3420/LT3420-1 charge high voltage photoflash
capacitors quickly and efficiently. Designed for use in both
digital and film cameras, these devices use a flyback
topology to achieve efficiencies up to four times better
than competing flash modules. A unique adaptive off-time
control algorithm* maintains current-limited continuous
mode transformer operation throughout the entire charge
cycle, eliminating the high inrush current often found in
modules.
The LT3420/LT3420-1 output voltage sensing scheme*
monitors the flyback voltage to indirectly regulate the
output voltage, eliminating an output resistor divider or
discrete zener diode. This feature allows the capacitor to
be held at a fully charged state without excessive power
consumption. Automatic refresh (which can be defeated)
allows the capacitor to remain charged while consuming
an average input current of about 2mA, at a user-defined
refresh rate. A logic high on the CHARGE pin initiates
charging, while the DONE pin signals that the capacitor is
fully charged.
The LT3420/LT3420-1 are available in 10-Lead MSOP and
(3mm × 3mm) DFN packages.
, LTC and LT are registered trademarks 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
T1
LT3420
0.1µF
51.1k
1:12
8
5,6
3,4
632
SW
SEC
R
REF
GND
1
7
PHOTOFLASH
1
2k
D1
220µF
330V
CAPACITOR
C3
+
V
BAT
1.8V TO 6V
INPUT CURRENT
≈350mA
V
2.5V TO 10V
CHARGE
DONE
C1, C2: 4.7µF, X5R or X7R, 10V
C3: RUBYCON 220µF PHOTOFLASH CAPACITOR
T1: TDK SRW10EPC-U01H003 FLYBACK TRANSFORMER
D1: VISHAY GSD2004S SOT-23
DUAL DIODE. DIODES CONNECTED IN SERIES
C1
4.7µF
V
BATRFB
C2
4.7µF
4
V
9
CHARGE
8
DONE
C
CC
T
10 5
CC
Figure 1. High Charge Rate LT3420 Photoflash Circuit
320V
DANGER HIGH VOLTAGE
OPERATION BY HIGH VOLTAGE
3420 F01
TRAINED PERSONNEL ONLY
T1
60.4k
LT3420-1
0.1µF
1:10
(3mm TALL)
4
3
632
SW
SEC
1
R
REF
GND
5
6
7
PHOTOFLASH
CAPACITOR
2k
D1
100µF
330V
320V
C3
+
3420 F02
V
BAT
1.8V TO 6V
INPUT CURRENT
≈450mA
V
2.5V TO 6V
CHARGE
DONE
C1, C2: 4.7µF, X5R or X7R, 6.3V
C3: RUBYCON 100µF PHOTOFLASH CAPACITOR
T1: KIJIMA MUSEN SBL-5.6S-2
D1: VISHAY GSD2004S SOT-23
DUAL DIODE. DIODES CONNECTED IN SERIES
C1
4.7µF
V
BATRFB
C2
4.7µF
4
V
9
CHARGE
8
DONE
C
CC
T
10 5
CC
Figure 2. Small Size LT3420-1 Photoflash Circuit
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1
LT3420/LT3420-1
WW
W
U
ABSOLUTE AXI U RATI GS
(Note 1)
V
Voltage .............................................................. 16V
CC
Voltage ............................................................ 16V
V
BAT
SW Voltage (Note 2)
LT3420 ................................................................ 38V
LT3420-1............................................................ 50V
SEC Current ...................................................... ±200mA
RFB Current ........................................................... ±3mA
R
Voltage ........................................................... 2.5V
REF
CHARGE Voltage...................................................... 16V
CT Voltage .............................................................. 1.5V
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PACKAGE/ORDER INFORMATION
TOP VIEW
R
1
REF
V
2
BAT
3
R
FB
4
V
CC
5
GND
10-LEAD (3mm × 3mm) PLASTIC DFN
T
JMAX
DD PACKAGE
= 125°C, θJA = 43°C/W, θJC = 3°C/W
EXPOSED PAD IS GND (PIN 11)
AND MUST BE SOLDERED TO PCB
10
C
CHARGE
9
11
DONE
8
7
SEC
6
SW
T
ORDER PART
NUMBER
LT3420EDD
LT3420EDD-1
DD PART
MARKING
LBJW
LBJX
DONE Voltage .......................................................... 16V
Current into DONE Pin .......................................... ±1mA
Maximum Junction Temperature .......................... 125°C
Operating Ambient Temperature Range
(Note 3) .............................................. –40°C to 85°C
Storage Temperature Range ................. –40°C to 125°C
Lead Temperature (Soldering, 10 sec)
(For MS Package only) ..................................... 300°C
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ORDER PART
TOP VIEW
1
R
REF
V
2
BAT
R
3
FB
V
4
CC
GND
5
MS PACKAGE
10-LEAD PLASTIC MSOP
T
= 125°C, θJA = 100°C/W, θJC = 45°C/W
JMAX
(4-LAYER BOARD)
10
9
8
7
6
C
T
CHARGE
DONE
SEC
SW
NUMBER
LT3420EMS
LT3420EMS-1
MS PART MARKING
LTYH
LTAJG
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifications are at TA = 25°C. VCC = V
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Operating Voltage, V
Maximum Operating Voltage, V
VCC UVLO Hysteresis 40 mV
Minimum V
Maximum V
V
UVLO Hysteresis 275 mV
BAT
R
Threshold Voltage 0.98 1.00 1.02 V
REF
R
Pin Bias Current V
REF
Quiescent Current V
Quiescent Current in Shutdown V
Voltage 1.6 1.8 V
BAT
Voltage 16 V
BAT
CC
CC
The ● denotes the specifications which apply over the full operating
= 3.3V, V
BAT
= 0V, Switching 2 4 µA
RREF
V
= V
RFB
RREF
CHARGE
– 0.2V (Note 4)
BAT
= 1.1V, Not Switching 90 130 µA
= 0V, VIN = 3.3V 0.01 1 µA
= VCC unless otherwise noted. (Note 3)
CHARGE
● 2.2 2.5 V
● 0.975 1.025 V
16 V
3420fb
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LT3420/LT3420-1
ELECTRICAL CHARACTERISTICS
temperature range, otherwise specifications are at T
The ● denotes the specifications which apply over the full operating
= 25°C. VCC = V
A
= 3.3V, V
BAT
= VCC unless otherwise noted. (Note 3)
CHARGE
PARAMETER CONDITIONS MIN TYP MAX UNITS
Primary Side Current Limit LT3420 (Note 5) 1.20 1.4 1.60 A
LT3420-1 (Note 5) 0.75 0.9 1.05 A
Secondary Side Current Limit LT3420 (Note 5) 20 40 50 mA
LT3420-1 (Note 5) 5 15 25 mA
Leakage Blanking Pulse Width LT3420 200 ns
LT3420-1 0 ns
Refresh Timer Charge/Discharge Current VCT = 0.75V 1.5 2.5 3.5 µA
Refresh Timer Upper Threshold 0.9 1.0 1.1 V
Refresh Timer Lower Threshold 0.45 0.5 0.55 V
Switch V
CESAT
LT3420, SW = 1A (Note 5) 220 340 mV
LT3420-1, SW = 0.5A (Note 5) 130 230 mV
Switch Leakage Current VSW = 38V (LT3420), VSW = 50V (LT3420-1) 0.01 1 µA
CHARGE Input Voltage High 1.5 V
CHARGE Input Voltage Low 0.2 V
CHARGE Pin Bias Current V
V
= 3V 4.5 15 µA
CHARGE
= 0V 0.01 0.1 µA
CHARGE
DONE Output Signal High 100k from VCC to DONE 3.3 V
DONE Output Signal Low 33µA into DONE Pin 100 200 mV
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Rated breakdown with LT3420 in power delivery mode and power
switch off.
Note 3: The LT3420/LT3420-1 are guaranteed to meet performance
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 4: Bias current flows out of R
Note 5: Current limit and V
to static test for DD package.
specifications from 0°C to 70°C. Specifications over the –40°C to 85°C
UW
TYPICAL PERFOR A CE CHARACTERISTICS
Graphs apply to both the LT3420 and LT3420-1 unless otherwise noted.
Output Voltage in Refresh Mode,
LT3420
335
330
325
320
(V)
315
OUT
V
310
305
300
295
–50
050
–25 25 75 125
TEMPERATURE (°C)
FIGURE 1 CIRCUIT
V
CC
V
BAT
= 3.3V
= 3.3V
100
3420 G01
Output Voltage in Refresh Mode,
LT3420
335
330
325
320
(V)
315
OUT
V
310
305
300
295
2.5
FIGURE 1 CIRCUIT
V
CC
V
BAT
TA = 25°C
4.03.53.0 5.55.04.5 6.0
VIN (V)
= V
= V
pin.
FB
guaranteed by design and/or correlation
CESAT
Charge Time, LT3420
10
FIGURE 1 CIRCUIT
UNLESS OTHERWISE
NOTED.
8
6
TIME (s)
4
C
= 100µF
OUT
IN
IN
3420 G02
2
0
2
V
CHARGED
OUT
FROM
50V TO 320V
= 25°C
T
A
C
= 220µF
OUT
453
V
(V)
BAT
6
3420 G03
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LT3420/LT3420-1
TEMPERATURE (°C)
–50
CURRENT (mA)
100
3420 G09
050
60
55
50
45
40
35
30
25
20
–25 25 75 125
TEMPERATURE (°C)
–50
CURRENT (mA)
100
3420 G12
050
35
30
25
20
15
10
5
–25 25 75 125
UW
TYPICAL PERFOR A CE CHARACTERISTICS
Graphs apply to both the LT3420 and LT3420-1 unless otherwise noted.
Output Voltage in Refresh Mode,
LT3420-1
335
330
325
320
(V)
315
OUT
V
310
305
300
295
–50
050
–25 25 75 125
TEMPERATURE (°C)
FIGURE 2 CIRCUIT
V
CC
V
BAT
Charge Pin Input Current
10
TA = 25°C
8
6
4
CURRENT (µA)
2
= 3.3V
= 3.3V
100
3420 G04
Output Voltage in Refresh Mode,
LT3420-1
335
330
325
320
(V)
315
OUT
V
310
305
300
295
2.5
FIGURE 2 CIRCUIT
V
V
TA = 25°C
VIN (V)
CC
BAT
Primary Current Limit, LT3420
1.7
1.5
1.3
CURRENT (A)
1.1
= V
IN
= V
IN
5.03.0 4.03.5 4.5 6.0
5.5
3420 G05
Charge Time, LT3420-1
10
8
6
TIME (s)
4
2
0
C
2
3
OUT
C
OUT
= 40µF
V
BAT
FIGURE 2 CIRCUIT
CHARGED
V
OUT
FROM 50V TO 320V
= 25°C
T
A
= 100µF
4
(V)
Secondary Current Limit, LT3420
5
6
3420 G06
4
0
2
34
CHARGE PIN VOLTAGE (V)
6
57 10
Efficiency of Figure 1 Circuit,
LT3420
90
TA = 25°C
V
OUT
VIN = 5V
(V)
80
VIN = 3.3V
70
60
EFFICIENCY (%)
50
40
50 150 350250
100 200 300
VCC = V
89
3420 G07
= V
BAT
IN
3420 G10
0.9
–25 25 75
–50
0
TEMPERATURE (°C)
50
Primary Current Limit, LT3420-1
1.2
1.1
1.0
CURRENT (A)
0.9
0.8
–25 25 75
–50
0
TEMPERATURE (°C)
50
100
100
125
3420 G08
Secondary Current Limit, LT3420-1
125
3420 G11
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TEMPERATURE (°C)
–50
V
BAT
PIN VOLTAGE (V)
100
3420 G18
050–25 25 75 125
2.0
1.8
1.6
1.4
1.2
1.0
V
+
V
–
ENABLE VOLTAGE
IS HYSTERETIC
TYPICAL PERFOR A CE CHARACTERISTICS
Graphs apply to both the LT3420 and LT3420-1 unless otherwise noted.
Efficiency for Figure 2 Circuit,
LT3420-1 Input Current, LT3420
90
TA = 25°C
80
70
60
EFFICIENCY (%)
50
40
50 150 350250
140
120
100
80
QUIESCENT CURRENT (µA)
60
2.5
VIN = 3.3V
100 200 300
V
TA = 25°C
4.0 7.0
5.5 8.5
VIN = 5V
(V)
OUT
VCC (V)
VCC = V
BAT
= V
IN
3420 G13
10
3420 G16
1000
FIGURE 1 CIRCUIT
= V
V
T
900
800
700
600
AVERAGE INPUT CURRENT (mA)
500
50 150 350250
V
2.6
2.5
2.4
2.3
2.2
2.1
PIN VOLTAGE (V)
CC
V
2.0
1.9
1.8
–50
= 3.3V
CC
BAT
= 25°C
A
100 200 300
V
OUT
Minimum Operating VoltageQuiescent Current in Refresh Mode V
CC
–
V
050
–25 25 75 125
TEMPERATURE (°C)
(V)
ENABLE VOLTAGE
IS HYSTERETIC
+
V
100
3420 G14
3420 G17
LT3420/LT3420-1
Input Current, LT3420-1
600
FIGURE 2 CIRCUIT
= V
V
550
T
500
450
400
AVERAGE INPUT CURRENT (mA)
350
300
50
= 3.3V
CC
BAT
= 25°C
A
150 200 250
100
Minimum Operating Voltage
BAT
V
(V)
OUT
300 350
3420 G15
3420fb
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LT3420/LT3420-1
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PI FU CTIO S
R
(Pin 1): Reference Resistor Pin. Place a resistor (R2)
REF
from the R
(Pin 2): Battery Voltage Input. This pin should be
V
BAT
connected to the power supply or battery, which supplies
power to transformer T1. Must be locally bypassed.
RFB (Pin 3): Feedback Resistor Pin. Place a resistor (R1)
from the SW pin to the R
following formula:
R
1
=++
R
1
=++
V
OUT
N: Transformer Turns Ratio
R
SEC
VD: Diode Forward Voltage Drop
pin to GND. 2k is recommended.
REF
pin. Set R1 according to the
FB
R
2
2
N
R
2
2
N
: Desired Output Voltage
: Transformer Secondary Resistance
RNV V
14 2
(. • ) ( )
[]
()( )
[]
SEC OUT D
RNV V
SEC OUT D
2
(LT3420)
(LT3420-1)
GND (Pin 5): Ground. Tie directly to local ground plane.
SW (Pin 6): Switch Pin. This is the collector of the internal
NPN power switch. Minimize the metal trace area connected to this pin to minimize EMI.
SEC (Pin 7): Transformer Secondary Pin. Tie one end of
the transformer secondary to this pin. Take care to use the
correct phasing of the transformer (Refer to Figures 1
and 2).
DONE (Pin 8): Done Output Pin. Open collector NPN
output. DONE is pulled low whenever the chip is delivering
power to the output and goes high when power delivery
stops.
CHARGE (Pin 9): Charge Pin. Drive CHARGE high (1.5V or
more) to commence charging of the output capacitor.
Drive to 0.2V or less to put the part in shutdown mode.
CT (Pin 10): Refresh Timer Capacitor Pin. Place a capacitor
from the CT pin to GND to set the refresh timer sample rate
according to the following formula:
R2: Resistor from the R
Choice
VCC (Pin 4): Input Supply Pin. Must be locally bypassed
with a 4.7µF or larger ceramic capacitor.
Pin to GND. 2k is a Typical
REF
CT = 2.5 • 10–6 • t
t
REFRESH
EXPOSED PAD (Pin 11) (DD Package only): GND. Must be
soldered to local ground plane on PCB.
: Desired Refresh Period in Seconds.
REFRESH
6
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