19-0728; Rev 4; 2/09
KIT
ATION
EVALU
BLE
AVAILA
Xenon Photoflash Charger with
IGBT Driver and Voltage Monitor
General Description
Features
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
2s to Charge 100µF to 300V
Integrated IGBT Driver
Voltage-Monitor Output*
Short-/Open-Circuit Protection
Controlled Inrush Current
Programmable Input Current Limit Up to 2A
(MAX8685A) or 2.6A (MAX8685F)*
Programmable Input Voltage-Overload Protection*
Extended Battery Life with Input-Voltage
Monitoring*
Internal 2.6A Switch
Robust Architecture Allows Use of Low-Cost
Transformers
High Accuracy Not Dependent on Transformer
Turns Ratio
Automatic Refresh Mode Draws Minimal
Quiescent Current
Charge-Done Indicator
3mm x 3mm, 14-Pin TDFN Package
(MAX8685A/MAX8685F)
2mm x 3mm, 8-Pin TDFN Package
(MAX8685C/MAX8685D)
MAX8685A/MAX8685C/MAX8685D/MAX8685F
The MAX8685 family charges high-voltage photoflash
capacitors quickly, while limiting peak drain from the
battery, through an efficient flyback switching regulator.
The internal n-channel MOSFET improves efficiency
over competing bipolar designs by lowering switch-
voltage dropout. An integrated insulated gate bipolar
transistor (IGBT) driver enables flash discharge and
reduces external component count. The device
includes an open-drain
DONE
output to indicate when
the photoflash voltage has reached regulation. The
device automatically refreshes the output voltage every
16s, thus efficiently maintains the capacitor charge
level with minimum battery drain.
The MAX8685A/MAX8685F feature an undervoltage
input (UVI) monitor. UVI monitors the supply voltage
and suspends switching if the input voltage drops
below a programmed threshold. The MAX8685A/
MAX8685F also feature a voltage-monitor output that
provides a scaled replica of the output voltage. The
voltage-monitor output is used for interfacing with a
microprocessor’s internal A/D converter to assist in
implementing red-eye reduction.
The MAX8685C/MAX8685D, with fixed peak-primary
current limits of 1A and 1.6A, respectively, are offered in
a 2mm x 3mm, 8-pin TDFN package. The MAX8685A/
MAX8685F, with resistor-programmable current limits of
up to 2A (max) and 2.6A (max), respectively, are offered
in a 3mm x 3mm, 14-pin TDFN package. All devices
operate over the -40°C to +85°C temperature range.
*MAX8685A/MAX8685F
only.
Ordering Information
PART
MAX8685AETD+
MAX8685CETA+
MAX8685DETA+
MAX8685FETD+
PIN-PACKAGE
14 TDFN-EP
†
3mm x 3mm
8 TDFN-EP
†
2mm x 3mm
8 TDFN-EP
†
2mm x 3mm
14 TDFN-EP
†
3mm x 3mm
TOP MARK
ADD
AAE
AAF
ADY
Typical Operating Circuit
V
BATT
+1.5V
TO
+10V
1:15
+300V
+
V
CC
+2.5V TO +5.5V
XENON
FLASH
TUBE
-
ISET UVI
V
CC
ISET
LX
SEC
FB
MAX8685A
MAX8685F
V
CCT
+2.5V
TO
+5.5V
MTR
V
CCT
GND
PGND
IGBT
Note:
All devices are specified over the -40°C to +85°C
operating temperature range.
+Denotes
a lead(Pb)-free/RoHS-compliant package.
†
EP= Exposed paddle.
Applications
Digital Cameras
Film Cameras
Cell-Phone Cameras
Personal Media Players
Pin Configurations appear at end of data sheet.
TRIG
GATE
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim's website at www.maxim-ic.com.
Xenon Photoflash Charger with
IGBT Driver and Voltage Monitor
MAX8685A/MAX8685C/MAX8685D/MAX8685F
ABSOLUTE MAXIMUM RATINGS
LX to PGND ............................................................-0.3V to +40V
EN, ISET, MTR, to GND ..............................-0.3V to (V
CC
+ 0.3V)
UVI to GND.............................................................-0.3V to +12V
V
CC
, V
CCT
, FB,
DONE
to GND .................................-0.3V to +6V
GATE, TRIG to PGND (MAX8685A/MAX8685F)
..............................................................-0.3V to (V
CCT
+ 0.3V)
GATE, TRIG to EP
(MAX8685C/MAX8685D).......................-0.3V to (V
CC
+ 0.3V)
PGND to GND (Note 1) .........................................-0.3V to +0.3V
SEC Current................................................................... ±200mA
Current into
DONE............................................................±10mA
Continuous Power Dissipation
8-Pin TDFN (derate 16.7mW/°C above T
A
= +70°C)
(multilayer PCB) ........................................................1333mW
14-Pin TDFN (derate 18.5mW/°C above T
A
= +70°C)
(single-layer PCB) .....................................................1481mW
14-Pin TDFN (derate 24.4mW/°C above T
A
= +70°C)
(multilayer PCB) ........................................................1951mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature Range ............................-40°C to +150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1:
For the MAX8685C/MAX8685D, GND and PGND are internally connected to the exposed paddle (EP). All references to GND
or PGND refer to the EP in the MAX8685C/MAX8685D.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= V
EN
= 3.3V, V
CCT
= 3.3V (MAX8685A/MAX8685F only); V
FB
= 0, R
ISET
= 93.1kΩ (MAX8685A), R
ISET
= 120kΩ (MAX8685F)
V
UVI
= 1.5V, T
A
= -40°C to +85°C, unless otherwise noted.) (Notes 2 and 3)
PARAMETER
V
CC
V
CC
Voltage Range
V
CC
Undervoltage Threshold
V
CC
Supply Current
V
CC
rising
V
CC
falling
Switching at 300kHz
Not switching
V
EN
= 0,
V
CC
= 5.5V,
V
TRIG
= 0
V
CCT
= 5.5V
V
CCT
= 0
T
A
= +25°C
T
A
= +85°C
T
A
= +25°C
T
A
= +85°C
T
A
= +25°C
T
A
= +85°C
V
CC
= 3.3V
V
CC
= 2.5V
T
A
= +25°C
T
A
= +85°C
R
ISET
= 93.1kΩ
ISET = V
CC
R
ISET
= 120kΩ
ISET = V
CC
MAX8685C
MAX8685D
1.4625
1.44
2.5
2.2
2.1
2.3
2.2
1.85
60
0.1
0.1
0.1
0.1
0.1
0.1
0.18
0.2
0.1
0.1
1.60
2.0
1.625
2.6
1.0
1.6
300
1.7875
1.76
0.4
0.5
1
1
µA
1
100
1
µA
5.5
2.4
2.3
V
V
mA
µA
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
Shutdown Current (MAX8685A/
MAX8685F)
V
CC
Shutdown Current
(MAX8685C/MAX8685D)
LX
LX On-Resistance
LX Off-Leakage
LX Peak Current Limit
(MAX8685A Only)
LX Peak Current Limit
(MAX8685F Only)
LX Peak Current Limit
LX Switching Frequency
V
EN
= 0, V
CC
= 5.5V,
V
TRIG
= 0
I
LX
= 190mA
V
LX
= 10V, V
EN
= 0
T
A
= 0°C to +85°C
T
A
= 0°C to +85°C
T
A
= 0°C to +85°C
Ω
µA
A
A
A
kHz
Circuit of Figure 3 or Figure 4, output 90%
of final value
2
_______________________________________________________________________________________
Xenon Photoflash Charger with
IGBT Driver and Voltage Monitor
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V
EN
= 3.3V, V
CCT
= 3.3V (MAX8685A/MAX8685F only); V
FB
= 0, R
ISET
= 93.1kΩ (MAX8685A), R
ISET
= 120kΩ (MAX8685F)
V
UVI
= 1.5V, T
A
= -40°C to +85°C, unless otherwise noted.) (Notes 2 and 3)
PARAMETER
SEC
SEC Sense Resistance
SEC Valley-Current Threshold (MAX8685A
Only)
SEC Valley-Current Threshold (MAX8685F
Only)
SEC Valley-Current Threshold
FB
FB Trip Threshold
FB Input Current
Output Refresh Rate
UVI (MAX8685A/MAX8685F only)
UVI Trip Threshold Falling
UVI Trip Threshold Rising
UVI Input Current
EN
EN Input Threshold
EN Input Leakage Current
V
EN
rising
V
EN
falling
V
EN
= 5.5V
V
CC
= 5.5V
V
FB
= 1.25V
V
FB
= 0.833V
V
FB
= 1.25V
T
A
= +25°C
T
A
= +85°C
1.94
1.280
0.4
1.0
0.9
5.5
5.5
2
1.333
100
2.06
1.387
10
1.4
V
µA
V
EN
= 0,
V
UVI
= V
CC
= 5.5V
T
A
= +25°C
T
A
= +85°C
0.98
1.05
1.00
1.07
0.1
0.1
1.02
1.09
1
V
V
µA
V
FB
rising
V
FB
= 1.25V
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= +85°C
1.24
1.237
1.25
1.250
0.1
0.1
16
1.26
1.263
1
V
µA
s
I
SEC
falling
I
SEC
falling
I
SEC
falling
R
ISET
= 93.1kΩ
ISET = V
CC
R
ISET
= 120kΩ
ISET = V
CC
MAX8685C
MAX8685D
1.1
21.4
26.7
10
16
16
16
Ω
mA
mA
mA
CONDITIONS
MIN
TYP
MAX
UNITS
MAX8685A/MAX8685C/MAX8685D/MAX8685F
From V
FB
> 1.25V to LX switching
VOLTAGE MONITOR (MAX8685A/MAX8685F only)
MTR Output Accuracy
MTR Output Current
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
DONE
DONE
Output Voltage, Low
DONE
Output Current, High
I
DONE
= 5mA
V
DONE
= 5.5V
T
A
= +25°C
T
A
= +85°C
100
0.1
0.1
400
1
mV
µA
170
15
°C
°C
V
µA
_______________________________________________________________________________________
3
Xenon Photoflash Charger with
IGBT Driver and Voltage Monitor
MAX8685A/MAX8685C/MAX8685D/MAX8685F
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V
EN
= 3.3V, V
CCT
= 3.3V (MAX8685A/MAX8685F only); V
FB
= 0, R
ISET
= 93.1kΩ (MAX8685A), R
ISET
= 120kΩ (MAX8685F)
V
UVI
= 1.5V, T
A
= -40°C to +85°C, unless otherwise noted.) (Notes 2 and 3)
PARAMETER
IGBT DRIVER
TRIG Input Thresholds
TRIG Input Current
GATE Source Current
GATE Sink Current
V
CCT
(MAX8685A/MAX8685F only)
V
CCT
Voltage Range
V
CCT
Shutdown Current
V
TRIG
= 0,
V
CCT
= 5.5V
T
A
= +25°C
T
A
= +85°C
2.5
0.1
0.1
5.5
1
V
µA
V
TRIG
rising
V
TRIG
falling
V
TRIG
= 5.5V
V
TRIG
= 3.3V
V
TRIG
= 0
T
A
= +25°C
T
A
= +85°C
0.4
5.5
5.5
250
50
10
1.4
V
µA
mA
mA
CONDITIONS
MIN
TYP
MAX
UNITS
Note 2:
For the MAX8685C/MAX8685D, GND and PGND are internally connected to the exposed paddle (EP). All references to GND
or PGND refer to the EP in the MAX8685C/MAX8685D.
Note 3:
Devices are 100% production tested at T
A
= +25°C. Limits over the operating temperature range are guaranteed by design
and characterization.
Typical Operating Characteristics
(V
EN
= V
BATT
= V
ISET
= V
CC
= 3.3V, V
CCT
= 5.5V, circuits of Figure 3, T
A
= +25°C, unless otherwise noted.)
CHARGE TIME (FROM 30V TO 300V)
vs. V
BATT
MAX8685A/C/D/F toc01
CHARGE TIME (FROM 30V to 300V)
vs. V
BATT
(MAX8685F)
MAX8685A/C/D/F toc02
CHARGE TIME (FROM 30V TO 300V)
vs. V
BATT
C
OUT
= 100μF
I
PEAK
= 2A
V
CC
= 2.5V
MAX8685A/C/D/F toc03
9
8
7
CHARGE TIME (s)
6
5
4
3
2
1
0
0
2
4
6
V
BATT
(V)
8
10
100μF
50μF
150μF
V
CC
= 5.5V
I
PEAK
= 2A
10
9
8
CHARGE TIME (s)
7
6
5
4
3
2
1
0
100μF
50μF
150μF
V
CC
= 5.5V
I
PEAK
= 2.6A
6.0
5.5
5.0
4.5
CHARGE TIME (s)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
CC
= 3.6V
V
CC
= 5V
12
0
2
4
6
8
10
0
1
2
3
4
5
6
7
8
9
10
V
BATT
(V)
V
BATT
(V)
4
_______________________________________________________________________________________
Xenon Photoflash Charger with
IGBT Driver and Voltage Monitor
Typical Operating Characteristics (continued)
(V
EN
= V
BATT
= V
ISET
= V
CC
= 3.3V, V
CCT
= 5.5V, circuits of Figure 3, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY
vs. OUTPUT VOLTAGE
MAX8685A/C/D/F toc04
MAX8685A/MAX8685C/MAX8685D/MAX8685F
OUTPUT VOLTAGE
vs. V
CC
V
BATT
= 5V
330
OUTPUT VOLTAGE (V)
320
310
300
290
280
MAX8685A/C/D/F toc05
OUTPUT VOLTAGE
vs. TEMPERATURE
325
OUTPUT VOLTAGE (V)
320
315
310
305
300
295
290
V
BATT
= 2.7V
V
BATT
= 3.3V
V
BATT
= 5V
MAX8685A/C/D/F toc06
100
90
80
EFFICIENCY (%)
70
60
50
40
30
50
100
150
200
250
V
BATT
= 5V
340
330
V
BATT
= 2.7V
V
BATT
= 3.3V
300
2.5
3.0
3.5
4.0
V
CC
(V)
4.5
5.0
5.5
-40
-15
10
35
60
85
OUTPUT VOLTAGE (V)
TEMPERATURE (°C)
PRIMARY CURRENT LIMIT
vs. R
ISET
MAX8685A/C/D/F toc07
PRIMARY CURRENT LIMIT
vs. R
ISET
(MAX8685F)
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
75
100
125
150
175
200
225
R
ISET
(kΩ)
MAX8685A/C/D/F toc08
PEAK PRIMARY CURRENT
vs. TEMPERATURE
2.4
PEAK PRIMARY CURRENT (A)
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
250
-40
-15
10
35
60
85
TEMPERATURE (°C)
ISET = V
CC
MAX8685A/C/D/F toc09
MAX8685A/C/D/F toc12
2.4
2.2
2.0
1.8
1.6
I
LIM
(A)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
75
100
125
150
175
200
225
2.5
250
R
ISET
(kΩ)
I
LIM
(A)
PEAK PRIMARY CURRENT
vs. V
CC
MAX8685A/C/D/F toc10
PEAK PRIMARY CURRENT
vs. V
CC
(MAX8685F)
ISET = V
CC
PEAK PRIMARY CURRENT (A)
2.5
2.0
1.5
1.0
0.5
TDK LDT565630T-041
0
R
ISET
= 100kΩ
MAX8685A/C/D/F toc11
UVI RISING THRESHOLD
vs. TEMPERATURE
1.20
1.18
1.16
UVI THRESHOLD (V)
1.14
1.12
1.10
1.08
1.06
1.04
1.02
1.00
V
CC
= 2.7V
V
CC
= 3.3V
V
CC
= 5V
3.0
2.5
2.0
1.5
1.0
0.5
0
2.5
3.0
3.5
4.0
V
CC
(V)
4.5
5.0
ISET = V
CC
3.0
PEAK PRIMARY CURRENT (A)
R
ISET
= 150kΩ
R
ISET
= 150kΩ
5.5
2.5
3.0
3.5
4.0
V
CC
(V)
4.5
5.0
5.5
-40
-15
10
35
60
85
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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