MAX8685AETD+T - Maxim Integrated

General Description

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.

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

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-0728; Rev 4; 2/09

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.

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.

EVALUATION KIT

AVAILABLE

PART PIN-PACKAGE

T O P M A R K

MAX8685AETD+ 14 TD FN - E P

†

3m m x 3m m ADD

MAX8685CETA+ 8 TD FN - E P

†

2mm x 3mm AAE

MAX8685DETA+ 8 TD FN - E P

†

2mm x 3mm AAF

MAX8685FETD+ 14 TD FN - E P

†

3mm x 3mm ADY

Pin Configurations appear at end of data sheet.

MAX8685A

MAX8685F

VCC

XENON

FLASH

TUBE

1:15 +300V

SEC

UVI LX

VBATT

+1.5V

+10V

VCC

+2.5V TO +5.5V ISET

MTR

VCCT

TRIG

GND

PGND

GATE IGBT

VCCT

+2.5V

+5.5V

ISET

Typical Operating Circuit

MAX8685A/MAX8685F only.

Applications

Digital Cameras

Film Cameras

Cell-Phone Cameras

Personal Media Players

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC = VEN = 3.3V, VCCT = 3.3V (MAX8685A/MAX8685F only); VFB = 0, RISET = 93.1kΩ(MAX8685A), RISET = 120kΩ(MAX8685F)

VUVI = 1.5V, TA= -40°C to +85°C, unless otherwise noted.) (Notes 2 and 3)

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.

LX to PGND ............................................................-0.3V to +40V

EN, ISET, MTR, to GND ..............................-0.3V to (VCC + 0.3V)

UVI to GND.............................................................-0.3V to +12V

VCC, VCCT, FB, DONE to GND .................................-0.3V to +6V

GATE, TRIG to PGND (MAX8685A/MAX8685F)

..............................................................-0.3V to (VCCT + 0.3V)

GATE, TRIG to EP

(MAX8685C/MAX8685D).......................-0.3V to (VCC + 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 TA= +70°C)

(multilayer PCB) ........................................................1333mW

14-Pin TDFN (derate 18.5mW/°C above TA= +70°C)

(single-layer PCB) .....................................................1481mW

14-Pin TDFN (derate 24.4mW/°C above TA= +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

PARAMETER CONDITIONS MIN TYP MAX UNITS

VCC

VCC Voltage Range 2.5 5.5 V

VCC rising 2.2 2.3 2.4

VCC Undervoltage Threshold VCC falling 2.1 2.2 2.3 V

Switching at 300kHz 1.85 mA

VCC Supply Current Not switching 60 100 µA

TA = +25°C 0.1 1

VCCT = 5.5V TA = +85°C 0.1

TA = +25°C 0.1 1

VCC Shutdown Current (MAX8685A/

MAX8685F)

VEN = 0,

VCC = 5.5V,

VTRIG = 0 VCCT = 0 TA = +85°C 0.1

µA

TA = +25°C 0.1 1

VCC Shutdown Current

(MAX8685C/MAX8685D)

VEN = 0, VCC = 5.5V,

VTRIG = 0 TA = +85°C 0.1 µA

VCC = 3.3V 0.18 0.4

LX On-Resistance ILX = 190mA VCC = 2.5V 0.2 0.5

TA = +25°C 0.1 1

LX Off-Leakage VLX = 10V, VEN = 0 TA = +85°C 0.1 µA

RISET = 93.1kΩ1.44 1.60 1.76

LX Peak Current Limit

(MAX8685A Only) TA = 0°C to +85°CISET = VCC 2.0 A

RISET = 120kΩ1.4625 1.625 1.7875

LX Peak Current Limit

(MAX8685F Only) TA = 0°C to +85°CISET = VCC 2.6 A

MAX8685C 1.0

LX Peak Current Limit TA = 0°C to +85°CMAX8685D 1.6 A

LX Switching Frequency Circuit of Figure 3 or Figure 4, output 90%

of final value 300 kHz

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.

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

_______________________________________________________________________________________ 3

PARAMETER CONDITIONS MIN TYP MAX UNITS

SEC

SEC Sense Resistance 1.1 Ω

RISET = 93.1kΩ21.4

SEC Valley-Current Threshold (MAX8685A

Only) ISEC falling ISET = VCC 26.7 mA

RISET = 120kΩ10

SEC Valley-Current Threshold (MAX8685F

Only) ISEC falling ISET = VCC 16 mA

MAX8685C 16

SEC Valley-Current Threshold ISEC falling MAX8685D 16 mA

TA = +25°C 1.24 1.25 1.26

FB Trip Threshold VFB rising TA = -40°C to +85°C 1.237 1.250 1.263 V

TA = +25°C 0.1 1

FB Input Current VFB = 1.25V TA = +85°C 0.1 µA

Output Refresh Rate From VFB > 1.25V to LX switching 16 s

UVI (MAX8685A/MAX8685F only)

UVI Trip Threshold Falling 0.98 1.00 1.02 V

UVI Trip Threshold Rising 1.05 1.07 1.09 V

TA = +25°C 0.1 1

UVI Input Current VEN = 0,

VUVI = VCC = 5.5V TA = +85°C 0.1 µA

VEN rising 1.0 1.4

EN Input Threshold VEN falling 0.4 0.9 V

TA = +25°C 5.5 10

EN Input Leakage Current VEN = 5.5V

VCC = 5.5V TA = +85°C 5.5 µA

VOLTAGE MONITOR (MAX8685A/MAX8685F only)

VFB = 1.25V 1.94 2 2.06

MTR Output Accuracy VFB = 0.833V 1.280 1.333 1.387 V

MTR Output Current VFB = 1.25V 100 µA

THERMAL SHUTDOWN

Thermal-Shutdown Threshold 170 °C

Thermal-Shutdown Hysteresis 15 °C

DONE

DONE Output Voltage, Low I DONE = 5mA 100 400 mV

TA = +25°C 0.1 1

DONE Output Current, High V DONE = 5.5V TA = +85°C 0.1 µA

ELECTRICAL CHARACTERISTICS (continued)

(VCC = VEN = 3.3V, VCCT = 3.3V (MAX8685A/MAX8685F only); VFB = 0, RISET = 93.1kΩ(MAX8685A), RISET = 120kΩ(MAX8685F)

VUVI = 1.5V, TA= -40°C to +85°C, unless otherwise noted.) (Notes 2 and 3)

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VCC = VEN = 3.3V, VCCT = 3.3V (MAX8685A/MAX8685F only); VFB = 0, RISET = 93.1kΩ(MAX8685A), RISET = 120kΩ(MAX8685F)

VUVI = 1.5V, TA= -40°C to +85°C, unless otherwise noted.) (Notes 2 and 3)

PARAMETER CONDITIONS MIN TYP MAX UNITS

IGBT DRIVER

VTRIG rising 1.4

TRIG Input Thresholds VTRIG falling 0.4 V

TA = +25°C 5.5 10

TRIG Input Current VTRIG = 5.5V TA = +85°C 5.5 µA

GATE Source Current VTRIG = 3.3V 250 mA

GATE Sink Current VTRIG = 0 50 mA

VCCT (MAX8685A/MAX8685F only)

VCCT Voltage Range 2.5 5.5 V

TA = +25°C 0.1 1

VCCT Shutdown Current VTRIG = 0,

VCCT = 5.5V TA = +85°C 0.1 µA

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 TA= +25°C. Limits over the operating temperature range are guaranteed by design

and characterization.

CHARGE TIME (FROM 30V TO 300V)

vs. VBATT

MAX8685A/C/D/F toc01

VBATT (V)

CHARGE TIME (s)

108642

012

VCC = 5.5V

IPEAK = 2A

150μF

100μF

50μF

0426810

CHARGE TIME (FROM 30V to 300V)

vs. VBATT (MAX8685F)

MAX8685A/C/D/F toc02

VBATT (V)

CHARGE TIME (s)

150μF

100μF

50μF

VCC = 5.5V

IPEAK = 2.6A

CHARGE TIME (FROM 30V TO 300V)

vs. VBATT

MAX8685A/C/D/F toc03

VBATT (V)

CHARGE TIME (s)

897546321

0.5

2.0

1.5

1.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

010

VCC = 2.5V

VCC = 3.6V

VCC = 5V

COUT = 100μF

IPEAK = 2A

Typical Operating Characteristics

(VEN = VBATT = VISET = VCC = 3.3V, VCCT = 5.5V, circuits of Figure 3, TA= +25°C, unless otherwise noted.)

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

_______________________________________________________________________________________

EFFICIENCY

vs. OUTPUT VOLTAGE

MAX8685A/C/D/F toc04

OUTPUT VOLTAGE (V)

EFFICIENCY (%)

250150 200100

100

50 300

VBATT = 5V

VBATT = 3.3V

VBATT = 2.7V

OUTPUT VOLTAGE

vs. VCC

MAX8685A/C/D/F toc05

VCC (V)

OUTPUT VOLTAGE (V)

4.53.5 4.03.0

300

290

310

320

330

340

280

2.5 5.55.0

VBATT = 5V

OUTPUT VOLTAGE

vs. TEMPERATURE

MAX8685A/C/D/F toc06

TEMPERATURE (°C)

OUTPUT VOLTAGE (V)

6010 35-15

305

300

295

310

315

320

325

330

290

-40 85

VBATT = 5V

VBATT = 3.3V

VBATT = 2.7V

PRIMARY CURRENT LIMIT

vs. RISET

MAX8685A/C/D/F toc07

RISET (kΩ)

ILIM (A)

225150 175 200100 125

1.0

0.8

0.6

0.2

0.4

1.2

1.4

1.6

1.8

2.2

2.0

2.4

75 250

PRIMARY CURRENT LIMIT

vs. RISET (MAX8685F)

MAX8685A/C/D/F toc08

RISET (kΩ)

ILIM (A)

225200150 175125100

0.4

0.2

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

75 250

PEAK PRIMARY CURRENT

vs. TEMPERATURE

MAX8685A/C/D/F toc09

TEMPERATURE (°C)

PEAK PRIMARY CURRENT (A)

10 35 60-15

1.9

1.8

1.6

1.7

2.0

2.1

2.2

2.4

2.3

2.5

1.5

-40 85

ISET = VCC

PEAK PRIMARY CURRENT

vs. VCC

MAX8685A/C/D/F toc10

VCC (V)

PEAK PRIMARY CURRENT (A)

4.5 5.03.5 4.03.0

1.0

0.5

1.5

2.0

2.5

3.0

2.5 5.5

ISET = VCC

RISET = 150kΩ

PEAK PRIMARY CURRENT

vs. VCC (MAX8685F)

MAX8685A/C/D/F toc11

VCC (V)

PEAK PRIMARY CURRENT (A)

5.04.54.03.53.0

0.5

1.0

1.5

2.0

2.5

3.0

2.5 5.5

ISET = VCC

RISET = 100kΩ

RISET = 150kΩ

TDK LDT565630T-041

UVI RISING THRESHOLD

vs. TEMPERATURE

MAX8685A/C/D/F toc12

TEMPERATURE (°C)

UVI THRESHOLD (V)

6010 35-15

1.02

1.06

1.04

1.08

1.10

1.12

1.14

1.16

1.18

1.20

1.00

-40 85

VCC = 2.7V

VCC = 3.3V

VCC = 5V

Typical Operating Characteristics (continued)

(VEN = VBATT = VISET = VCC = 3.3V, VCCT = 5.5V, circuits of Figure 3, TA= +25°C, unless otherwise noted.)

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VEN = VBATT = VISET = VCC = 3.3V, VCCT = 5.5V, circuits of Figure 3, TA= +25°C, unless otherwise noted.)

QUIESCENT CURRENT

vs. VCC

MAX8685A/C/D/F toc13

VCC (V)

IQ (μA)

5.04.53.5 4.03.0

100

150

200

250

300

2.5 5.5

EN = VCC

EN = GND

VCCT = VBATT = 3.3V

SWITCHING WAVEFORMS

MAX8685A/C/D/F toc14

1μs/div

ILX 2A/div

VLX 20V/div

ISEC 100mA/div

2μs/div

SWITCHING WAVEFORMS (MAX8685F)

ILX

ISEC

200mA/div

1A/div

20V/div

MAX8685A/C/D/F toc15

VLX

CHARGE PROFILE

COUT = 100μF

MAX8685A/C/D/F toc17

1s/div

VDONE

VOUT

VEN

10V/div

100V/div

5V/div

VLX

VCC = VBATT = 5V

LINE STEP WITH UVI

VOUT = 300V; RUVI = 75kΩ

MAX8685A/C/D/F toc16

20ms/div

VBATT 200mV/div

ILX 1A/div

200ms/div

CHARGE PROFILE (MAX8685F)

COUT = 35μF

VDONE

VEN

VLX

20V/div

5V/div

100V/div

MAX8685A/C/D/F toc18

VOUT

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

_______________________________________________________________________________________ 7

Typical Operating Characteristics (continued)

(VEN = VBATT = VISET = VCC = 3.3V, VCCT = 5.5V, circuits of Figure 3, TA= +25°C, unless otherwise noted.)

CHARGE-UP WAVEFORM OF MTR

MAX8685A/C/D/F toc19

1s/div

500mV/div

VMTR

100V/div

VOUT

MTR OUTPUT IMPEDANCE = 12kΩ

200ms/div

CHARGE-UP WAVEFORM OF MTR

(MAX8685F)

VOUT 100V/div

500V/div

MAX8685A/C/D/F toc20

VMTR

IGBT DRAIN AND GATE WAVEFORMS

MAX8685A/C/D/F toc21

10ms/div

VGATE

2V/div

100V/div

VDG

STARTUP INTO

SHORT-CIRCUIT WAVEFORMS

MAX8685A/C/D/F toc22

4s/div

VLX

ILX 500mA/div

2V/div

100mV/div

VMTR

OUTPUT OPEN-CIRCUIT WAVEFORMS

MAX8685A/C/D/F toc23

1μs/div

VLX

ILX 1A/div

10V/div

FIRST CHARGE CYCLE

MAX8685A/C/D/F toc24

2μs/div

VLX

ILX 1A/div

10V/div

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

8 _______________________________________________________________________________________

Pin Description

MAX8685A/

MAX8685F

MAX8685C/

MAX8685D

NAME FUNCTION

11EN

Enable Input. Drive EN high to turn on the charger or low to turn it off. EN is internally pulled

to GND through a 1MΩ resistor.

2 — GND Analog Ground. Connect GND directly to PGND and the exposed paddle in a star ground

configuration.

3 2 TRIG IGBT Driver Trigger Input. Drive TRIG to VCCT (VCC) to trigger GATE. TRIG is internally

pulled to PGND through a 1MΩ resistor.

4—V

CCT Supply Voltage Connection for the IGBT Driver. Bypass VCCT to PGND with a 1µF ceramic

capacitor. Connect VCCT to VCC or an external supply up to 5.5V maximum.

5 3 GATE

IGBT Driver Output. Connect GATE to the IGBT gate. The GATE output voltage swings

between VCCT and PGND (MAX8685A/MAX8685F only). For the MAX8685C/MAX8685D,

the GATE output voltage swings between VCC and PGND (EP).

6 — PGND Power Ground. Connect PGND directly to GND and the exposed paddle in a star ground

configuration.

74DONE

Charge Done Indicator. DONE is an open-drain output that is internally pulled low when EN

is driven high and the output capacitor is charged. DONE is high impedance when EN is

driven low (shutdown mode) and while the output capacitor is charging.

85LX

Transformer Primary Connection. Connect LX to the transformer primary as shown in Figure

3 or Figure 4. In shutdown mode, the internal switch is off and LX is connected to the

battery voltage through the primary side of the transformer. An internal clamp limits the LX

voltage to 34V.

9 6 SEC Secondary Current-Sense Input. Connect SEC to the return of the secondary winding to

measure current.

10 — UVI

Battery Input Undervoltage Detect. Connect a resistor from UVI to the battery to make a

resistor-divider with an internal 75kΩ resistor to GND. The input current from the battery is

reduced when VUVI drops below 1V. Connect UVI to VCC when this feature is not in use.

UVI is high impedance when EN is driven low (shutdown mode).

11 — ISET

Current-Limit Set. Connect a resistor from ISET to GND to set the peak current limit through

the primary winding. For the MAX8685A, RISET = 2A x 75kΩ / IPEAK. For the MAX8685F,

RISET = 2.6A x 75kΩ / IPEAK. Connect ISET to VCC to set the current limit to 2A (MAX8685A)

or to 2.6A (MAX8685F).

12 7 VCC Supply Voltage for the IC. Bypass VCC to GND (EP) with a 1µF ceramic capacitor.

13 8 FB Outp ut Feed b ack. C onnect FB to the center of a r esi stor - d i vi d er connected b etw een the

tr ansfor m er ’ s second ar y w i nd i ng and GN D to set the outp ut vol tag e. V

FB r eg ul ates to 1.25V .

14 — MTR

Voltage-Monitor Output. The sample-and-hold monitor circuitry provides a voltage

proportional to the output voltage. MTR provides a 2V output when VFB equals 1.25V. The

voltage monitor output is only valid when the part is charging. In shutdown mode, MTR is

internally grounded. See the Output-Voltage Monitoring (MAX8685A/MAX8685F Only)

section.

——EP

Exposed Paddle. Connect the exposed paddle, GND, and PGND together. Note that the

exposed paddle is the only ground connection for the MAX8685C/MAX8685D.

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

_______________________________________________________________________________________ 9

MAX8685A

MAX8685F

+OP

COMP

SAMPLE-AND-HOLD

CIRCUITRY

1.0V

DONE

MTR

75kΩ

VCC

1.0V

ISET

UVI

TRIG

GATE

IGBTDRV

100kΩ

VCCT

+2.5V

+5.5V

16s

23μs

250ns

DRV

VCC

+2.5V TO +5.5V

VBATT

+1.5V TO +10V

SEC

PGND

1.25V

1.1Ω

+300V

GND

COMP

Figure 1. MAX8685A/MAX8685F Functional Diagram

Detailed Description

The MAX8685 family of devices utilizes a flyback DC-DC

converter topology with current-limited continuous-mode

(CCM) control scheme and internal switch to charge

photoflash capacitors quickly and efficiently. Low-

battery-detection circuitry monitors the input voltage on a

cycle-by-cycle basis and reduces peak primary current

if the input voltage decreases below the UVI threshold.

An integrated IGBT driver with internal pullup and

pulldown resistors safely drives IGBTs for discharging the

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

10 ______________________________________________________________________________________

MAX8685C

MAX8685D

+OP

COMP

1.0V

DONE

16s

23μs

250ns

DRV

VCC

+2.5V TO +5.5V VBATT

+1.5V TO +10V

SEC

1.25V

1.1Ω

R16

R18

+300V

TRIG

GATE

IGBTDRV

100kΩ

VCC

Figure 2. MAX8685C/MAX8685D Functional Diagram

output capacitor through a xenon flash bulb. A voltage-

monitor output generates a sampled replica of the output

voltage to interface with the microprocessor’s internal A/D

converter to assist in implementing red-eye reduction.

Figure 1 shows the MAX8685A/MAX8685F functional

diagram; Figure 2 is the functional diagram for the

MAX8685C/MAX8685D.

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

______________________________________________________________________________________ 11

MAX8685A

MAX8685F

ISET

VCC

FT1

XENON

FLASH

TUBE

R7A

1MΩ

100μF

330V

1kΩ

248kΩ

10μF

1:15

1:43.5

0.022μF

630V

+300V

SEC

LXUVI

VBATT

1.5V TO 10V

VCC

+2.5V TO +5.5V

DONEDONE

MTR

VCCT

TRIGTRIG

MTR

ENEN

GATE

1μF

1nF

402Ω

R14

1kΩ

75kΩT1

GND

PGND

1μF

Figure 3. MAX8685A/MAX8685F Typical Application Circuit

Control Scheme

The MAX8685 family uses a constant peak-and-valley

current-control scheme to precisely control the

photoflash capacitor charging current. The MAX8685A/

MAX8685F current limit is set by the ISET resistor (see

the

Choosing a Resistor for Lowering the Charge

Current (MAX8685A/MAX8685F Only)

section) or by

connecting ISET to VCC for a maximum limit of 2A

(MAX8685A) or 2.6A (MAX8685F). The resistor at ISET

(MAX8685A/MAX8685F) and the transformer turns ratio

set the peak charge current.

The MAX8685C/MAX8685D offer fixed peak primary cur-

rent limits of 1A and 1.6A, respectively. Drive EN high to

turn on the LX switch and initiate charging. After the LX

switch turns on, the current in the transformer primary

winding increases to the peak current limit. When the LX

switch turns off, the energy stored in the transformer is

delivered to the photoflash capacitor through the trans-

former secondary and rectifying diode. As the sec-

ondary current ramps down, it is monitored through

SEC. When the current drops to 1.67% of the primary

peak current limit, the LX switch turns on after a 50ns

delay (MAX8685C/MAX8685D/MAX8685F) and a new

charge cycle begins. There is no delay in the

MAX8685A. This cycle repeats itself, adding energy to

the photoflash capacitor until the target output voltage is

reached. The switching frequency is determined by the

time required to ramp the primary-side inductance to

the LX peak current limit and the discharge time of the

secondary current. The switching frequency increases

as the output capacitor charges to the targeted output

voltage. Once the target output voltage is reached, the

IC automatically refreshes the output every 16s, effi-

ciently maintaining the capacitor charge level with mini-

mum battery drain. The MAX8685 family draws only

60µA (typ) in automatic refresh mode. Automatic

refresh can be overridden by driving EN low.

Secondary-Side Sensing

Output regulation is accomplished using a resistor-

divider connected to the anode of the output rectifying

diode (see Figure 3 or Figure 4). This connection elimi-

nates DC current drain on the output capacitor while

still providing direct output sensing for optimum voltage

accuracy that is not dependent on the transformer turns

ratio. The MAX8685 samples VFB during the flyback

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

12 ______________________________________________________________________________________

phase (when the LX switch is off). When VFB rises

above 1.25V, charging stops and DONE internally pulls

low. See the

Adjustable Output Voltage

section for

information on selecting values for the resistor-divider.

Extending Battery Life

with UVI (MAX8685A/MAX8685F Only)

The UVI circuit allows the output to charge as fast as

possible without causing the input voltage to drop

below a programmed voltage level. This feature permits

the current limit to be set for a faster charge rate under

typical conditions, rather than a level dictated by worst-

case discharge state of the battery. The UVI compara-

tor determines if the input source is being pulled low as

a result of the input current drawn by photoflash charg-

ing or some other process in the camera. When UVI

drops below the UVI falling threshold, the LX control

latch is reset and the internal MOSFET is immediately

turned off. The LX switch remains off until the current in

the transformer secondary drops to the valley trip

threshold, or for 1µs, whichever occurs first. To reduce

average charge current, the LX switch only turns on if

the input is above the UVI rising threshold.

Photoflash Capacitor Fault Protection

The MAX8685 family features protection circuitry to

detect an open- or short-circuited output capacitor.

During a normal charge cycle, after EN is driven high,

the MAX8685 devices generate the first LX pulse with a

peak primary current limit equal to one-half the pro-

grammed peak current limit with all subsequent pulses

equal to the programmed peak current limit.

In the event that the output capacitor is open circuited

(see the Output Open-Circuit Waveforms diagram in

the

Typical Operating Characteristics

), the first LX

pulse charges up the parasitic capacitance at the

transformer secondary above the targeted output volt-

age. Since the FB error amplifier is satisfied, no other

switching cycles occur until the autorefresh timer

expires after 16s. At this point, if EN is still high, the

MAX8685 generates another LX pulse with half the

peak current limit. This feature helps to protect the main

switch when the output capacitor is open circuited.

In the event that the output capacitor is short circuited

(see the Startup into Short-Circuit Waveforms diagram

in the

Typical Operating Characteristics

), the first (half-

amplitude) LX pulse does not increase the output volt-

age, so normal LX switching occurs for the full 16s. If

the output voltage has not reached its expected final

voltage at this point, the MAX8685 stops switching, but

the internal reference circuit remains on. This feature

helps limit battery drain in the event the output capaci-

tor is short circuited. Cycling EN or VCC allows another

charge cycle to occur.

MAX8685C

MAX8685D

VCC

R20A

1MΩ

R18

1kΩ

R16

248kΩ

C14

10μF

1:15

+300V

SEC

VBATT

+1.5V TO +10V

VCC

+2.5V TO +5.5V

DONEDONE

TRIG

TRIG GATE

1μF

R19

402Ω

C10

100μF

330V

1:43.5

C12

0.022μF

630V T4

FT2

XENON

FLASH

TUBE

Figure 4. MAX8685C/MAX8685D Typical Application Circuit

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

______________________________________________________________________________________ 13

UVLO

The MAX8685 family of devices provides a UVLO thresh-

old for the VCC power-supply input. When VCC < VUVLO,

the device cannot turn on. All switching behavior is locked

out until VCC increases above the UVLO threshold.

Operation near the UVLO threshold can result in slight

overcharge of the output capacitor. Additionally, the

voltage-monitor output (VMTR) may not provide a prop-

er output voltage when VCC is near the UVLO threshold

and less than the minimum valid VCC voltage in the

Electrical Characteristics

table. To ensure that this does

not occur, always connect the MAX8685 family of

devices to a valid VCC voltage in accordance with the

Electrical Characteristics

Applications Information

IGBT Driver

The MAX8685 family provides an integrated IGBT dri-

ver to trigger and control the discharge of the

photoflash capacitor through a xenon flash bulb.

Internal pullup and pulldown resistors control the turn-

on and turn-off rate of the IGBT. The MAX8685A/

MAX8685F provides a separate power input (VCCT) for

the IGBT driver, while the IGBT drivers of the

MAX8685C/MAX8685D use VCC as their power source.

Drive TRIG high to turn on the IGBT gate. Drive TRIG

low to turn off the IGBT gate. An internal 1MΩpulldown

resistor on TRIG prevents indeterminate states on the

input, while an internal 100kΩpulldown resistor on

GATE prevents indeterminate states on the IGBT gate

in the event that VCCT is not present.

The IGBT driver circuitry remains active when EN is

pulled low and VCC is valid. This allows a reduction in

battery-power consumption, while the photoflash

capacitor is being discharged through the xenon flash

tube. However, EN may be left high so that multiple

flashes at maximum intensity can occur in rapid suc-

cession, if needed.

IGBT Selection

IGBT selection is important for long-term reliability of

the photoflash-discharge circuitry. Ensure that the

IGBT’s VCE maximum voltage rating exceeds the maxi-

mum expected output voltage at the photoflash capaci-

tor. Additionally, choose an IGBT that can withstand

peak currents in excess of 150A.

Choose an IGBT such that its VGE specification over the

expected VCCT (or VCC) voltage range is met. Failure to

observe these specifications can result in damage to

the IGBT. Observe the grounding recommendations in

the IGBT data sheet because many IGBTs have a sepa-

rate emitter connection for the GATE drive only.

Output-Voltage Monitoring

(MAX8685A/MAX8685F Only)

A voltage monitor provides a scaled replica of the output

voltage in real time. The scaled output voltage interfaces

with a microprocessor’s internal A/D converter. MTR

provides a 2V output when VFB equals 1.25V. The volt-

age-monitor output is only valid when the part is charg-

ing. In shutdown mode, MTR is internally grounded.

Transformer Design

The transformer is a key element in any transformer fly-

back design. The switching elements are subject to

significantly large voltage and current stresses,

depending on the transformer design. The transformer

also plays a key role in the noise performance of the

circuit. Proper selection, design, and construction of

the transformer are crucial to the performance of a

photoflash charger.

Minimum Transformer Turns Ratio

The transformer turns ratio needs to be high enough so

that the transformer’s peak primary voltage does not

exceed the voltage rating (34V) of the clamp on the

internal MOSFET. The minimum transformer turns ratio

is determined by:

where VOUT is the output voltage, VDis the diode volt-

age drop, and VBATT is the battery voltage. For example,

VOUT = 300V, VD= 2.0V, VBATT = 1.5V. The equation

above provides a minimum turns ratio of 1:10. A trans-

former with a turns ratio of 1:15 is typically recommend-

ed for most applications.

Primary Inductance

The MAX8685 family operates either in discontinuous-

conduction mode (DCM) or in continuous-conduction

mode (CCM). Generally, CCM operation offers a higher

efficiency and lower ripple currents for the same output

power as compared to DCM operation. The capacitive

switching losses in the DMOS switch are minimal at the

boundary of DCM and CCM operation. The primary

inductance is therefore estimated based on this CCM

assumption. The MAX8685 devices have a maximum

on-time limit (tON(MAX)), typically 23µs, and a typical

peak current limit (ILIM). The maximum inductance for a

minimum battery voltage (VBATT(MIN)) is given by:

LVt

PRI MAX BATT MIN ON MAX

LIM

() () ( )

=×

NVV

OUT D

BATT

−34

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

14 ______________________________________________________________________________________

Secondary Inductance

The boundary of DCM and CCM operation is deter-

mined by monitoring the secondary valley current. The

secondary current-sensing circuit in the MAX8685 fami-

ly has a blanking time of approximately 250ns, resulting

in a minimum off-time (tOFF(MIN)). Since the minimum

discharge time occurs at the target output voltage

VOUT(MAX), the minimum secondary inductance is

given by:

where N is the transformer turns ratio. This in turn implies

a minimum primary inductance LPRI(MIN) given by:

Choose a value between LPRI(MIN) and LPRI(MAX)

based on other considerations for the leakage induc-

tance and the transformer capacitance. A transformer

with a primary inductance of 6µH is recommended for

most applications.

Leakage Inductance

A particularly important transformer parameter is leakage

inductance. In a practical transformer construction, all

windings cannot be equally well-coupled to the core

because of physical separation. If the primary inductance

is high, the transformer may need multiple windings for

the primary. A small amount of energy is stored in the

leakage inductance. If the primary inductance is too

small, the primary windings may not cover the width of

the core and result in poor coupling to the secondary.

This also increases the leakage inductance. Leakage

inductance does not participate in the primary to sec-

ondary energy transfer. Since the leakage inductance

does not find a path for the current built up during the

switch on-time, it results in voltage spikes and ringing at

the drain of the MAX8685 internal power switch (LX) when

it turns off.

The MAX8685 family’s internal switch is designed to be

robust to withstand these voltage spikes; however, volt-

age overshoot needs to be minimized because it

reduces total efficiency. Leakage inductance also

delays the transfer of power from input to output, caus-

ing an increase in charge time. In addition, transformer

secondary leakage inductance may couple with the

reverse recovery current of the output rectifier diode to

cause ringing when the diode turns off. The transformer

secondary leakage inductance and the capacitance of

the rectifier determine this resonant frequency. There is

typically very little loss in the resonant circuit, so this

network can generate many cycles of ringing after the

spike. The ringing can therefore affect the peak primary

current-sense signal.

The transformer secondary leakage inductance is a

function of the primary leakage inductance. Care must

be taken during transformer design while applying

techniques such as sandwiching the secondary

between two primary windings to minimize leakage

inductance. This can cause high winding-to-winding

capacitance, reducing the efficiency of the circuit, and

increasing the charge time.

Transformer Secondary Capacitance

The total capacitance on the secondary must be mini-

mized for both efficient and proper operation. Since the

secondary of the transformer undergoes large voltage

swings, capacitance on the secondary is a significant

detriment to efficiency. This capacitance is reflected on

the primary as an effective capacitance proportional to

the square of the transformer turns ratio. It therefore

dominates the resulting capacitance on the primary.

Both the leakage inductance and the secondary

capacitance of the transformer need to be minimized

for efficient operation.

Rectifying Diode

The rectifying diode(s) must have sufficient reverse

voltage and forward-current ratings. The peak-reverse

voltage VR(PEAK) seen by the diode(s) is given by:

The peak current of the diode IS(PEAK) is determined by

the peak primary current as:

Rectifier capacitance and transformer secondary leak-

age inductance couple to cause ringing when the

diode turns off. The overshoot caused by this ringing

can exceed the diode voltage rating and cause dam-

age to the diode. The ringing can also affect the cur-

rent-sense signal in the MAX8685 devices. Therefore, it

is recommended that the rectifying diode have very low

capacitance of 5pF or less. The transition from the con-

duction to the blocking state recovery time is trr.

The reverse recovery time must be as small as possible

to reduce losses due to this reverse current. The

reverse recovery voltage spikes also generate noise

that can interfere with the current-sense signal. The

MAX8685C/MAX8685D/MAX8685F add a 50ns delay

S PEAK LIM

()

VV NV

R PEAK OUT MAX BATT() ()

=+×

PRI MIN SEC MIN

() ()

LVNt

SEC MIN OUT MAX OFF MIN

LIM

() () ()

=××

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

______________________________________________________________________________________ 15

on each switching cycle to reduce losses during

reverse recovery. The slope of the voltage spike for

recovery from the peak reverse current to 0A is used to

characterize the diode as a soft recovery type if the

slope is small, or a hard recovery type if the slope is

steep. A soft recovery diode exhibits significantly lower

switching noise than a hard recovery type. Snubbers

can be used to make the reverse recovery waveform

soft, but they also lower efficiency. A diode with a small

trr and soft recovery is definitely an advantage.

Recommended diodes are listed in Table 1.

Adjustable Output Voltage

The MAX8685 family uses secondary feedback to

sense the output voltage (see Figure 3 or Figure 4). The

output voltage is set by the ratio of a resistor voltage-

divider. Choose the lower resistor (R3 in Figure 3 or

R18 in Figure 4), connected from FB to GND, less than

2kΩ. A typical value for R3 (R18) is 1kΩ. Larger resistor

values combined with parasitic capacitance at FB can

slow the rise time of the FB voltage during each cycle.

This can prevent the feedback circuitry from detecting

when the output has reached the desired level.

The value for the upper resistor (R1 in Figure 3 or R16

in Figure 4) is found from:

where VFB is 1.25V. Make sure the voltage rating of the

resistors is sufficient. It may be necessary to use two

resistors in series for the upper resistor so as not to

exceed the resistor voltage rating.

Capacitor Selection

The VCC, VCCT, and VBATT decoupling capacitors are

preferred to be multilayer ceramic type with X5R or X7R

dielectric for use across a wide temperature range. Use

of Y5V and Z5U dielectrics is strongly discouraged due

to the higher voltage and temperature coefficient of

these materials.

Choosing a Resistor for Lowering

the Charge Current

(MAX8685A/MAX8685F Only)

Set the default for the peak-primary current limit in the

MAX8685A/MAX8685F by connecting ISET to VCC. The

default peak current limit is 2A for the MAX8685A and

2.6A for the MAX8685F. This current limit works well for

most applications where the fastest photoflash charge

time is desired. If a lower current is required, connect a

resistor (R4 in Figure 1) from ISET to GND. Select R4 as

follows:

Adjusting the Battery Threshold for

Lowering Charge Current

(MAX8685A/MAX8685F Only)

The UVI circuit allows a camera to be ready to flash in a

short time when the battery is fresh, while still allowing

flash pictures when the battery is at low capacity by

extending the charge time to limit the battery surge cur-

rent. If the UVI input voltage drops below the falling

threshold (1.0V typ), the LX switch turns off. On a cycle-

by-cycle basis, the input current decreases so that the

input remains at or above the UVI threshold until charg-

ing is complete. Set the UVI falling threshold by con-

necting a resistor (R5 in Figure 3) between UVI and the

battery input to form a voltage-divider with an internal

75kΩresistor. Select the UVI resistor value as follows:

where VUVI is 1V and VBATT(MIN) is the desired mini-

mum operating battery voltage. When VCC is connect-

ed to VBATT, the UVI falling threshold must be set to

2.5V or higher. The operational range of R5 is from

37.5kΩto 675kΩ.

DONE

Output

DONE is an open-drain output that internally pulls low

when EN is high and the circuit has finished charging

the output capacitor. Once the output capacitor is

charged, DONE remains low until EN or VCC goes low.

To use DONE as a logic-level output, connect a pullup

BATT MIN

UVI

575 1=× −

⎛

⎝

⎜⎞

⎠

⎟

Ω()

Ik MAX A

Ik MAX F

LIMIT

420 75 8685

426 75 8685

=×

.()

RRV

OUT

13 1=−

⎛

⎝

⎜⎞

⎠

⎟

PART SUPPLIER

MAXIMUM

REVERSE

VOLTAGE

(V, EACH)

CAPACITANCE

(pF, EACH)

BAV23S (Dual) Philips 250 5

BAW101S

(Dual) Philips 300 2

CMPD2004S

(Single) Central 240 5

CMPD20055

(Single) Central 300 5

Table 1. Recommended Diodes

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

16 ______________________________________________________________________________________

resistor (typically 100kΩ) from DONE to the logic sup-

ply rail. DONE can also drive an LED by placing it in

series with a resistor (Figures 3 and 4). When driving

an LED, select the series resistor value so that the cur-

rent into DONE is less than 10mA. Note that when the

output capacitor is fully charged, the MAX8685 family

autorefreshes every 16s as long as EN is high.

Layout Guidelines

Warning: Lethal voltages are present in this circuit.

Use caution when working with this circuit.

The high-voltage/high-current operation of this applica-

tion demands careful attention to board layout. Larger

than minimum space between traces in the high-voltage

area is recommended. This is essential to meet the volt-

age-breakdown specifications of the board. To minimize

the high-frequency noise generated by switching, high

dV/dt paths must be made as short as possible to

reduce radiated noise. A high di/dt loop creates noise

due to radiated magnetic fields. To reduce high di/dt

loop-generated noise, make the loop as small as possi-

ble. Keep the area for the high-voltage end of the sec-

ondary as small as possible. Refer to the MAX8685

evaluation kit for a layout example.

A proper grounding scheme is critical for overall perfor-

mance and long-term reliability of the MAX8685 family

of devices. Create separate ground planes for GND,

PGND, and the photoflash discharge ground. First, cre-

ate a GND plane close to the MAX8685 for the feed-

back resistor connection, VCC bypass capacitor, ISET

resistance (MAX8685A/MAX8685F only), and MTR

(MAX8685A/MAX8685F only) output filter. Connect this

ground plane to the GND pin (MAX8685A/MAX8685F

only) and the exposed paddle of the device. In the

case of the MAX8685C/MAX8685D, the exposed pad-

dle is the only ground connection on the device.

Next, create a power ground plane for the photoflash

capacitor charging components. Bypass VCCT

(MAX8685A/MAX8685F only) and battery ground return

to this power ground plane and connect to the PGND

pin of the device (MAX8685A/MAX8685F only). In the

case of the MAX8685C/MAX8685D, the exposed pad-

dle also serves as the PGND connection. Connect

PGND to GND using a single point near the MAX8685.

Lastly, create a separate power ground for the high-

current discharge path. The photoflash capacitor, IGBT

emitter (pins 1 and 2), and trigger transformer ground

connection should all connect to the discharge ground

plane. Connect the discharge ground plane to PGND

near the MAX8685 PGND pin using the Kelvin-sense

emitter connection provided on the IGBT (pin 3). This

forces a single-point ground for the discharge path and

provides a good return path for the IGBT driver cur-

rents and photoflash capacitor charging currents.

It is important to note that when the photoflash capaci-

tor is discharged, there is a very fast di/dt that induces

a voltage spike on the ground plane. Failure to observe

proper grounding techniques can result in damage to

the MAX8685 or other components in the circuit.

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

______________________________________________________________________________________ 17

Chip Information

PROCESS: BiCMOS

MAX8685A

MAX8685F

TDFN

3mm × 3mm

TOP VIEW

245

13 11 10

ISET

UVI

GND

VCCT

GATE

MTREN

VCC

TRIG

SECPGND

LXDONE

+EXPOSED PADDLE

NOTE: EXPOSED PADDLE IS GND FOR THE MAX8685C/MAX8685D.

865

FB SEC LX

MAX8685C

MAX8685D

VCC

EN GATE

EXPOSED PADDLE

DONETRIG

TDFN

2mm × 3mm

Pin Configurations

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

18 ______________________________________________________________________________________

6, 8, &10L, DFN THIN.EPS

Package Information

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

14 TDFN-EP T1433-2 21-0137

8 TDFN-EP T823-1 21-0174

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

______________________________________________________________________________________ 19

COMMON DIMENSIONS

SYMBOL MIN. MAX.

A 0.70 0.80

D 2.90 3.10

E 2.90 3.10

A1 0.00 0.05

L 0.20 0.40

PKG. CODE N D2 E2 eJEDEC SPEC b[(N/2)-1] x e

PACKAGE VARIATIONS

0.25 MIN.k

A2 0.20 REF.

2.00 REF0.25±0.050.50 BSC2.30±0.1010T1033-1

2.40 REF0.20±0.05- - - - 0.40 BSC1.70±0.10 2.30±0.1014T1433-1

1.50±0.10 MO229 / WEED-3

0.40 BSC - - - - 0.20±0.05 2.40 REFT1433-2 14 2.30±0.101.70±0.10

T633-2 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF

T833-2 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF

T833-3 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF

2.30±0.10 MO229 / WEED-3 2.00 REF0.25±0.050.50 BSC1.50±0.1010T1033-2

Package Information (continued)

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

20 ______________________________________________________________________________________

8L, TDFN.EPS

PACKAGE OUTLINE

21-0174 2

8L TDFN, EXPOSED PAD, 2x3x0.8mm

Package Information (continued)

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

______________________________________________________________________________________ 21

SYMBOL

DIMENSIONS

3.002.95

0.75

NOM.

0.70

MIN.

0.20 REF.

0.40

0.02

2.00

0.30

0.00

1.95

k 0.20 MIN.

PACKAGE OUTLINE

21-0174

8L TDFN, EXPOSED PAD, 2x3x0.8mm

3.05

0.80

MAX.

0.50

0.05

2.05

0.50 BSC

b0.250.18 0.30

1.60

MIN.

1.75

NOM.

1.90

MAX.

1.50

MIN.

1.63

NOM.

1.75

MAX.

T823-1

PKG.

CODE

EXPOSED PAD PACKAGE

Package Information (continued)

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

MAX8685A/MAX8685C/MAX8685D/MAX8685F

Xenon Photoflash Charger with

IGBT Driver and Voltage Monitor

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Revision History

REVISION

NUMBER

REVISION

DATE DESCRIPTION PAGES

CHANGED

4 2/09 Added information regarding the clamp on LX 8, 9, 10, 13

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