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A8439-DS, Rev. 1
The A8439 is a highly integrated IC that charges
photoflash capacitors for digital and film cameras. An
integrated MOSFET switch drives the transformer in
a flyback topology. It also features an integrated IGBT
driver that facilitates the flash discharge function and
saves board space.
The CHARGE pin enables the A8439 and starts the
charging of the output capacitor. When the designated
output voltage is reached, the A8439 stops the charg-
ing until the CHARGE pin is toggled again. Pulling
the CHARGE pin low stops the charging. The D O N E
pin is an open-drain indicator of when the designated
output voltage is reached.
The peak current limit can be adjusted to eight dif-
ferent levels between 270 mA to 1.4 A, by clocking
the CHARGE pin. This allows the user to operate the
flash even at low battery voltages.
The A8439 can be used with two Alkaline/NiMH/
NiCAD or one single-cell Li+ battery connected to the
transformer primary. Connect the VIN pin to a 3.0 to
5.5 V supply, which can be either the system rail or the
Li+ battery, if used.
The A8439 is available in a very low profile
(0.75 mm) 10-terminal 33 mm MLP/TDFN package,
making it ideal for space-constrained applications. It is
lead (Pb) free, with 100% matte-tin leadframe plating.
Photoflash Capacitor Charger
with IGBT Driver and Refresh
A8439
Package EJ:
MLP/TDFN, 3 3 mm
0.75 mm Nominal Height
FEATURES
APPLICATIONS
Power with 1 Li+ or 2 Alkaline/NiMH/NiCAD batteries
Adjustable output voltage
Autorefresh
>75% efficiency
Eight-level, digitally-programmable current limit
Charge complete indication
Integrated IGBT driver with trigger
No primary-side Schottky diode needed
Low-profile package (0.75 mm nominal height)
Digital camera flash
Film camera flash
Cell phone flash
Emergency strobe light
Approximate Scale 1:1
Figure 1. Typical circuit with separate power supply to transformer
Figure 2. Typical circuit with single power supply
To IGBT Gate
COUT
V
OUT
D1
T1
R1
R2
R3
One Li+ battery
or 3.0 to 5.5 V
V
BATT
C2
4.7 F
C3
C1
0.1 F
100 k
R4
A8439
CHARGE
GND
FB
SW
TRIGGER
IGBTDRV
DONE
VIN
+
To IGBT Gate
COUT
V
OUT
D1
T1
R1
R2
R3
100 k
R4
V
BATT
Two Alkaline/NiMH/NiCAD or one Li+ battery
or 1.5 to 5.5 V
V
BIAS
3.0 to 5.5 V
C2
4.7 F
C1
0.1 F
A8439
CHARGE
GND
FB
SW
TRIGGER
IGBTDRV
DONE
VIN
C3
A8439-DS, Rev. 1
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Photoflash Capacitor Charger with IGBT Driver
A8439
2
Functional Block Diagram
VIN
VIN
SW
CHARGE
GND
CMP2
DONE
FB
Q
I
LIM
Decoder
Adjustable
Reference
IGBTDRV
TRIGGER
1.2 V
40 V
DMOS
Q
Q
SET
CLR
S
R
CMP3
CMP1
1.2 V
I
LIM
Comparator
DCM
Comparator
H L
Triggered Timer
Control Logic
Enable
18 s
Terminal List Table
Ab so lute Max i mum Rat ings
10
9
8
7
6
NC
FB
DONE
TRIGGER
SW
1
2
3
4
5
NC
IGBTDRV
VIN
GND
CHARGE
Device Pin-out Diagram
R
JA
= 45 C/W, on a 4-layer board. Additional information is
available on the Allegro Web site.
Package Thermal Characteristics
Number
Name
Function
1,10
NC
No connection
2
IGBTDRV IGBT driver gate drive output
3
VIN
Power supply input
4
GND
Device ground
5
CHARGE
Charging enable and ISWLIM code
input; set to low to power-off the A8439
6
SW
Switch, internally connected to the
DMOS power FET drain
7
TRIGGER Strobe signal input
8
D O N E
Open drain, when pulled low by internal
MOSFET, indicates that charging target
level has been reached
9
FB
Output voltage feedback
Input or Output Voltage
SW
pin,
V
SW
............................................................ 0.3 to 40 V
IGBTDRV
pin,
V
IGBTDRV
.............................. 0.3 to V
IN
+ 0.3 V
FB
pin,
V
FB
............................................................... 0.3 to V
IN
All other pins, V
x
...................................................... 0.3 to 7 V
Operating Ambient Temperature, T
A
................................ 40C to 85C
Maximum Junction Temperature, T
J(max)
........................................ 150C
Storage Temperature, T
S
.............................................. 55C to 150C
A8439-DS, Rev. 1
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Photoflash Capacitor Charger with IGBT Driver
A8439
3
ELECTRICAL CHARACTERISTICS
Typical values at T
A
= 25C and V
IN
= 3.3 V (unless otherwise noted)
Characteristics
Symbol
Test Conditions
Min.
Typ. Max. Units
Supply Voltage*
V
IN
3
5.5
V
Supply Current
I
IN
Charging
1.5
mA
Charging done / Refresh monitoring
300
600
A
Shutdown (V
CHARGE
= 0 V, V
TRIGGER
= 0 V)
0.01
1
A
Primary Side Current Limit
(ILIM clock input at CHARGE pin)
I
SWLIM1
1.2
1.4
1.6
A
I
SWLIM2
1.2
A
I
SWLIM3
1.0
A
I
SWLIM4
0.86
A
I
SWLIM5
0.7
A
I
SWLIM6
0.55
A
I
SWLIM7
0.4
A
I
SWLIM8
0.27
A
SW On Resistance
R
DS(On)SW
V
IN
= 3.3 V, I
D
= 800 mA, T
A
= 25C
0.27
SW Leakage Current*
I
SWLKG
V
SW
= 35 V
1
A
SW Maximum Off-Time
t
OFF(Max)
18
s
CHARGE Input Current
I
CHARGE
V
CHARGE
= V
IN
1
A
CHARGE Input Voltage*
V
CHARGE(H)
2
V
V
CHARGE(L)
0.8
V
ILIM Clock High Time at
CHARGE Pin
t
ILIM(H)
0.2
s
ILIM Clock Low Time at
CHARGE Pin
t
ILIM(L)
0.2
s
Total ILIM Setup Time
t
ILIM(SU)
60
s
D O N E Output Leakage Current*
I
DONELKG
1
A
D O N E Output Low Voltage*
V
DONE(L)
32 A into D O N E pin
100
mV
FB Voltage Threshold*
V
FB
1.187 1.205 1.223
V
FB Input Current
I
FB
V
FB
= 1.205 V
120
nA
UVLO Enable Threshold
V
UVLO
V
IN
rising
2.55
2.65
2.75
V
UVLO Hysteresis
V
UVLOHYS
150
mV
IGBT Driver
IGBTDRV On Resistance to VIN
R
DS(On)I-V
V
IN
= 3.3 V, V
IGBTDRV
= 1.5 V, V
TRIGGER
= V
IN
5
IGBTDRV On Resistance to GND
R
DS(On)I-G
V
IN
= 3.3 V, V
IGBTDRV
= 1.5 V, V
TRIGGER
= 0 V
6
TRIGGER Input Current
I
TRIGGER
V
TRIGGER
= V
IN
1
A
TRIGGER Input Voltage*
V
TRIGGER(H)
2
V
V
TRIGGER(L)
0.8
V
Propagation Delay, Rising
t
Dr
R
gate
=12 , C
LOAD
= 6500 pF, V
IN
= 3.3 V
30
ns
Propagation Delay, Falling
t
Df
R
gate
=12 , C
LOAD
= 6500 pF, V
IN
= 3.3 V
30
ns
Output Rise Time
t
r
R
gate
=12 , C
LOAD
= 6500 pF, V
IN
= 3.3 V
70
ns
Output Fall Time
t
f
R
gate
=12 , C
LOAD
= 6500 pF, V
IN
= 3.3 V
70
ns
*Guaranteed by design and characterization over operating temperature range, 40C to 85C.
A8439-DS, Rev. 1
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Photoflash Capacitor Charger with IGBT Driver
A8439
4
Performance Characteristics
Tests performed using application circuit shown in figure 8
with I
SWLIM
set to 1.4A (Single rising edge on CHARGE pin), unless otherwise noted
Charging Waveforms
Symbol
Parameter Units/Division
C1
V
OUT
50 V
C4
I
BATT(Avg)
200 mA
t
time
1 s
Conditions
Parameter
Value
V
BATT
2.5 V
V
BIAS
3.3 V
C
OUT
100 F
Symbol
Parameter Units/Division
C1
V
OUT
50 V
C4
I
BATT(Avg)
200 mA
t
time
1 s
Conditions
Parameter
Value
V
BATT
3.6 V
V
BIAS
3.3 V
C
OUT
100 F
Symbol
Parameter Units/Division
C1
V
OUT
50 V
C4
I
BATT(Avg)
200 mA
t
time
1 s
Conditions
Parameter
Value
V
BATT
4.2 V
V
BIAS
3.3 V
C
OUT
100 F
t
I
BATT
V
OUT
C4
C1
t
I
BATT
V
OUT
C4
C1
t
I
BATT
V
OUT
C4
C1
A8439-DS, Rev. 1
Worcester, Massachusetts 01615-0036 (508) 853-5000
115 Northeast Cutoff, Box 15036
www.allegromicro.com
Allegro MicroSystems, Inc.
Photoflash Capacitor Charger with IGBT Driver
A8439
5
V
OUT
(V)
Efficiency (%)
V
BATT
(V)
Charge T
ime (s)
100
150
200
250
300
350
40
50
60
80
70
90
2.0
2.5
3.0
3.5
4.0
4.5
5.0
V
OUT
= 300 V
V
OUT
= 320 V
5.5
6.0
V
BATT
= 4.2 V
V
BATT
= 5.0 V
2
4
3
5
7
6
8
V
BATT
= 3.0 V
2
3
4
5
6
7
8
2
2.5
3
3.5
4
4.5
5
5.5
6
V
BATT
(V)
C
h
a
r
ge
Tim
e
(
s
)
V
OUT
= 300 V
V
OUT
= 320 V
Charge Time
V
BIAS
= 3.3 V, C
OUT
= 100 F
Connect VBATT to a separate power supply
Efficiency
V
BATT
= V
BIAS
, T
A
= 25C
Typical Switching Waveform
Performance Characteristics, continued
Tests performed using application circuit shown in figure 8
with I
SWLIM
set to 1.4A (Single rising edge on CHARGE pin), unless otherwise noted
IGBTDRV
TRIGGER
t
Dr
t
r
t
Df
t
f
50%
10%
90%
50%
10%
90%
IGBT Drive Timing Definition
Symbol
Parameter Units/Division
C1
V
OUT
50 V
C2
V
SW
10 V
C3
V
BATT
5 V
C4
I
Primary
500 mA
t
time
2 s
Conditions
Parameter
Value
V
OUT
300 V
V
BATT
V
IN
t
V
BATT
V
OUT
C4
C1
C3
C2
V
SW
I
Primary
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