A8735
Ultra Small Mobile Phone Xenon Photoflash
Capacitor Charger with IGBT Driver
Discontinued Product
This device is no longer in production. The device should not be
purchased for new design applications. Samples are no longer available.
Date of status change: December 3, 2013
Recommended Substitutions:
For existing customer transition, and for new customers or new appli-
cations, contact Allegro Sales.
NOTE: For detailed information on purchasing options, contact your
local Allegro field applications engineer or sales representative.
Allegro MicroSystems, LLC reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The
information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no respon-
sibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
A8735
Ultra Small Mobile Phone Xenon Photoflash
Capacitor Charger with IGBT Driver
Features and Benefits
▪
Ultra small 2 × 2 DFN/MLP-8 package
▪
Low quiescent current draw (0.5
μA
max. in shutdown mode)
▪
Primary-side output voltage sensing; no resistor divider required
▪
Fixed 1 A peak current limit
▪
1V logic (V
HI
(min)) compatibility
▪
Integrated IGBT driver with internal gate resistors
▪
Optimized for mobile phone, 1-cell Li+ battery applications
▪
Zero-voltage switching for lower loss
▪
>75% efficiency
▪
Charge complete indication
▪
Integrated 50 V DMOS switch with self-clamping protection
Description
The Allegro
™
A8735 is a Xenon photoflash charger IC designed
to meet the needs of ultra low power, small form factor cameras,
particularly camera phones. By using primary-side voltage
sensing, the need for a secondary-side resistive voltage divider
is eliminated. This has the additional benefit of reducing leakage
currents on the secondary side of the transformer. To extend
battery life, the A8735 features very low supply current draw
(0.5
μA
max in shutdown mode). The IGBT driver also has
internal gate resistors for minimum external component count.
The charge and trigger voltage logic thresholds are set at 1
V
HI
(min) to support applications implementing low-voltage
control logic.
The A8735 is available in an 8-contact 2 mm × 2 mm
DFN/MLP package with a 0.60 maximum overall package
height, and an exposed pad for enhanced thermal performance.
It is lead (Pb) free with 100% matte tin leadframe plating.
Package: 8-pin DFN/MLP (suffix EE)
2 mm × 2 mm, 0.60 mm height
Not to scale
Typical Applications
Battery Input
2.3 to 5.5 V
VBAT
VOUT Detect
SW
VIN_VDRV
C2
Control
Block
+
C1
COUT
100F
315 V
Battery Input
1.5 to 5.5 V
VBAT
+
C1
COUT
100F
315 V
VOUT Detect
SW
VIN_VDRV
Control
Block
I
SW
sense
VPULLUP
C2
I
SW
sense
VPULLUP
CHARGE
DONE
DONE
VIN_VDRV
100 kΩ
CHARGE
DONE
DONE
VIN_VDRV
100 kΩ
TRIG
IGBT Driver
IGBT Gate
GATE
TRIG
IGBT Driver
IGBT Gate
GATE
GND
GND
(A)
Figure 1. Typical applications: (A) with single battery supply and (B) with separate bias supply
8735-DS
(B)
A8735
Ultra Small Mobile Phone Xenon Photoflash
Capacitor Charger with IGBT Driver
Selection Guide
Part Number
A8735EEETR-T
Packing
3000 pieces per reel
Package
8-contact DFN/MLP with exposed thermal pad
Absolute Maximum Ratings
Characteristic
Symbol
Notes
DC voltage.
(V
SW
is self-clamped by internal active clamp
and is allowed to exceed 50 V during flyback
spike durations. Maximum repetitive energy
during flyback spike: 0.5
μJ
at frequency
≤
400 kHz.)
DC current, pulse width = 1 ms
Care should be taken to limit the current when
–0.6 V is applied to these pins.
T
A
T
J
(max)
T
stg
Range E
Rating
Units
SW Pin
V
SW
–0.3 to 50
V
I
SW
VIN_DRV, VBAT Pins
¯ ¯ ¯¯
CHARGE, TRIG, ¯ ¯ ¯ ¯ Pins
DONE
Remaining Pins
Operating Ambient Temperature
Maximum Junction
Storage Temperature
V
IN
3
–0.3 to 6.0
–0.6 to V
IN
+ 0.3 V
–0.3 to V
IN
+ 0.3 V
–40 to 85
150
–55 to 150
A
V
V
V
ºC
ºC
ºC
THERMAL CHARACTERISTICS may require derating at maximum conditions
Characteristic
Package Thermal Resistance
Symbol
R
θJA
Test Conditions*
4-layer PCB, based on JEDEC standard
Value Units
49
ºC/W
*Additional thermal information available on Allegro Web site.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A8735
Ultra Small Mobile Phone Xenon Photoflash
Capacitor Charger with IGBT Driver
Functional Block Diagram
VBAT
SW
V
SW
– V
BAT
DCM
Detector
t
off
(max)
18
μs
S
Q
Q
Control Logic
DMOS
ILIM
Reference
V
DS
ref
OCP
t
on
(max)
18
μs
H
L
Triggered Timer
R
Enable
VIN_DRV
S
R
Q
DONE
Q
CHARGE
VIN_DRV
IGBT Driver
TRIG
GATE
GND
Terminal List
Number
Name
¯¯ ¯¯
¯ ¯ ¯¯
DONE
TRIG
GATE
GND
SW
VBAT
VIN_DRV
CHARGE
PAD
Function
Open collector output, pulls low when output reaches target value and CHARGE is
high. Goes high during charging or whenever CHARGE is low.
IGBT trigger input.
IGBT gate drive output.
Ground connection.
Drain connection of internal DMOS switch. Connect to transformer primary winding.
Battery voltage.
Input voltage. Connect to 3 to 5.5 V bias supply. Decouple V
IN
voltage with 0.1
μF
ceramic capacitor placed close to this pin.
Charge enable pin. Set this pin low to shut down the chip.
Exposed pad for enhanced thermal dissipation. Connect to ground plane.
Pin-out Diagram
DONE 1
TRIG 2
GATE 3
GND 4
PAD
8
7
6
5
CHARGE
VIN_DRV
VBAT
SW
1
2
3
4
5
6
7
8
–
(Top View)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A8735
Ultra Small Mobile Phone Xenon Photoflash
Capacitor Charger with IGBT Driver
indicates specifications
Min.
1.5
2.3
V
IN
rising
Shutdown (CHARGE = 0 V, TRIG = 0 V)
–
–
–
–
–
–
–
–
0.9
V
IN_DRV
= 3.6 V, I
D
= 600 mA, T
A
= 25°C
V
SW
= 5.5, over full temperature range
V
CHARGE
= V
IN
High, over input supply range
Low, over input supply range
Time between CHARGE = 1 and charging
enabled
–
–
–
1.0
–
–
–
–
Measured as V
SW
– V
BAT
Pulse width = 200 ns (90% to 90%)
¯ ¯ ¯¯
32
μA
into ¯ ¯ ¯ ¯ pin
DONE
Measured at SW pin
Input = logic high, over input supply range
Input = logic low, over input supply range
V
GATE
= 1.8 V
V
GATE
= 1.8 V
¯ ¯ ¯¯
Measurement taken at ¯ ¯ ¯ ¯ pin,
DONE
C
L
= 6500 pF
31.0
–
Charging complete
Charging (CHARGE = V
IN
, TRIG = 0 V)
Shutdown (CHARGE = 0 V, TRIG = 0 V)
Typ.
–
–
2.05
150
0.02
50
2
0.01
–
–
1.0
0.4
–
36
–
–
20
18
18
31.5
200
Max.
5.5
5.5
2.2
–
0.5
100
–
1
5
50
1.1
–
2
–
–
0.4
–
–
–
32.0
400
1
–
–
1
–
–
–
–
–
–
–
–
–
–
20
–
–
100
21
27
25
60
290
380
20
100
–
–
0.4
–
–
–
–
–
–
–
–
Unit
V
V
V
mV
μA
μA
mA
μA
μA
μA
A
Ω
μA
μA
V
V
us
μs
μs
V
mV
μA
mV
V/μs
V
V
kΩ
Ω
Ω
ns
ns
ns
ns
kΩ
Characteristics
Symbol
V
BAT
V
IN
V
INUV
V
INUV(hys)
I
IN
Test Conditions
guaranteed from
−40°C
to 85°C ambient, unless otherwise noted
VBAT Voltage Range
1
VIN_DRV Voltage Range
1
UVLO Enable Threshold
UVLO Hysteresis
V
IN
Supply Current
ELECTRICAL CHARACTERISTICS
Typical values are valid at V
IN
= V
BAT
= 3.6 V; T
A
= 25°C, except
VBAT Pin Supply Current
I
BAT
Charging done (CHARGE = V
IN
,
¯ ¯ ¯ ¯ = 0 V)
¯ ¯ ¯¯
DONE
Charging (CHARGE = V
IN
, TRIG = 0 V)
Current Limit
Primary-Side Current Limit
2
Switch On-Resistance
Switch Leakage Current
1
CHARGE Input Current
CHARGE Input Voltage
1
CHARGE On/Off Delay
Switch-Off Timeout
Switch-On Timeout
Output Comparator Trip Voltage
3
Output Comparator Voltage Overdrive
¯ ¯ ¯ ¯ Output Leakage Current
1
¯ ¯ ¯¯
DONE
¯ ¯ ¯ ¯ Output Low Voltage
1
¯ ¯ ¯¯
DONE
dV/dt Threshold for ZVS Comparator
IGBT Driver
TRIG Input Voltage
1
TRIG Pull-Down Resistor
GATE Resistance to VIN_DRV
GATE Resistance to GND
Propagation Delay (Rising)
4,5
Propagation Delay (Falling)
4,5
Output Rise Time
4,5
Output Fall Time
4,5
GATE Pull-Down Resistor
1
Specifications
2
Current
I
SWLIM
R
SWDS(on)
I
SWLK
I
CHARGE
V
CHARGE
t
CH
t
off(max)
t
on(max)
V
OUTTRIP
V
OUTOV
I
DONELK
V
DONEL
dV/dt
V
TRIG(H)
V
TRIG(L)
R
TRIGPD
R
SrcDS(on)
R
SnkDS(on)
t
Dr
t
Df
t
r
t
f
R
GTPD
throughout the range T
A
= –40°C to 85°C guaranteed by design and characterization.
limit guaranteed by design and correlation to static test.
3
Specifications throughout the range T = –20°C to 85°C guaranteed by design and characterization.
A
4
Guaranteed by design and characterization.
5
See IGBT Drive Timing Definition diagram for further information.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
模拟电子
