CAP-XX APPEB1006 User Manual

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User’s Manual

Camera Phone Flash

Evaluation Board

APPEB1006

All information contained herein is strictly confidential APPEB1006 User Manual rev1.0, 31-May-2005 page 1 of 6

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All information contained herein is strictly confidential APPEB1006 User Manual rev1.0, 31-May-2005 page 2 of 6

Camera Phone Flash Evaluation Board User’s Manual

Board Features

FLASH mode with adjustable voltage and current TORCH/MOVIE mode with adjustable voltage and current Vin and Vout indicating LED’s On-board or External triggering On-board or External white LED LED and inductor current measurement ability Undervoltage lockout (UVLO) Boost enable/disable during flash and torch for different power architectures Auto run for flash or torch

Quick Setup

The following jumpers should be in place J2, J5, J7, J8 and J10. Connect the positive terminal of a single cell Lithium Ion rechargeable battery (3.3V-4.2V) to any pin on J1 and connect the negative terminal to any pin of J3. The red LED (D1) should come on immediately and the yellow LED (D2) should increase in brightness over a few seconds whilst the supercapacitor charges up.

When the TORCH push button (SW1) is pressed 100mA will flow through the white LED (D5). At 100mA the button can be held down continuously.

When the FLASH push button (SW2) is pressed 1A will flow through the white LED (D5) for approximately 80ms. If the button is held down continuously the flash will retrigger approximately every 2.5s. This duty cycle is imposed due to the thermal constraints of the white LED.

Circuit Description (refer to schematics at the end of this manual)

Input Voltage

The circuit is designed to operate from an external Li ion battery (4.2V-3.3V). Vbat is the node connected to the battery via J1.

J1 is to be connected to battery positive terminal. Pins 1 and 2 of J1 are joined. J3 is to be connected to battery negative terminal. Pins 1 and 2 of J3 are joined.

An undervoltage lockout (UVLO) has been included (U2B) such that when the battery voltage drops below 3.1V the main switch (MOSFET M1) opens. It will reclose with 350mV of hysteresis (3.45V). The 3V regulator remains operational during a UVLO.

The main reason for the UVLO is that the boost controls Vout which is the sum of the input voltage (battery or perhaps bench top supply) plus the supercap (C1) voltage. The voltage across the supercap is not measured. Therefore, if the input voltage was say 3V and Vout was controlled to be 5.7V then the supercap would be at 2.7V which reduces its life. For maximum life the supercap should be kept below 2.3V. However, the supercapacitor voltage can be increased to 2.5V for short periods, such as while taking flash photos, without affecting life.

Indicating LED’s

D1 is a red LED that indicates a source voltage is present and that a UVLO has not occurred. D2 is a yellow LED and indicates that Vout is present and above approximately 5V.

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All information contained herein is strictly confidential APPEB1006 User Manual rev1.0, 31-May-2005 page 3 of 6

Boost Converter

J2 needs to be jumpered for normal operation. This jumper has been included so a wire loop can easily be inserted to measure the inductor current. By measuring the inductor current and monitoring the base drive voltage of Q1 the current through Q1, D3 and supercap can also be determined.

J4 is not jumpered during normal operation. This jumper has been included to manually disable the boost if required. If jumpered it forces the feedback voltage at pin 6 of the boost to be 3V which is >> than the 730mV of the internal reference thereby instructing the boost to cease switching.

The boost can also be disabled by pulling the gate of M3 low. This can be done automatically during a FLASH pulse by jumpering J7 or while in TORCH mode by jumpering J10.

The advantage of disabling the boost during a FLASH pulse is that the maximum battery current is equal to the load (flash LED) current, however, the disadvantage is that the supercap discharge current is also equal to the load current and it will discharge at a faster rate than if the boost was enabled. The disadvantage of enabling the boost during a Flash pulse is that the maximum battery current is greater or much greater then the load current depending on the current limit set on the boost.

FLASH MODE

The boost generates an output voltage (Vout) that is > the battery voltage. For FLASH mode, Vout is factory set to 5.7V. This voltage can be increased by turning R17 (a 2k pot) anticlockwise. Care must be taken if this voltage is increased not to overvoltage the supercap, ie the supercap voltage will be Vout minus the voltage of the battery. For maximum supercapacitor life the voltage should be kept below 2.3V however short term overvoltages (seconds) may go up to 2.7V.

TORCH MODE

The continuous current required for TORCH is << FLASH current (typically 100mA Vs 1A). Therefore the voltage dropped across the LED will be less. To increase efficiency (and to reduce thermal stress on the current limiting MOSFET (M4)) Vout should also be reduced.

There are two options for the TORCH Vout, if constant high output light is more important than efficiency then option a) should be chosen.

a) In this option the Boost is enabled with J10 removed and J11 is jumpered. Vout can

be adjusted using R12 (a 500k pot). Vout is factory set to 4.2V. This means that Vout will always be > Vin irrespective of the battery voltage. In this mode the forward voltage to drive the LED at 200mA, for example, will always be available even when the battery nears its end voltage (3.3V).

b) In this option the Boost is disabled with J10 jumpered and J11 is don’t care. This

means Vout will always be equal to Vin minus the drops incurred by the inductor’s (L1) DC resistance and D3. This is the most efficient mode because the current limiting MOSFET (M4) does not have to drop as many volts and the Boost is not operating. However, depending on the LED current required, there may not be enough voltage headroom in Vout when the battery nears its end voltage (3.3V). For example, if the LED current was chosen to be 200mA and the voltage across a typical LED at this current was also 3.3V then there would be no volts available across the current sense resistor (R22) and M4 and then only say 150mA would be available. Option b) is factory chosen and the TORCH current is set to 100mA.

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All information contained herein is strictly confidential APPEB1006 User Manual rev1.0, 31-May-2005 page 4 of 6

The user must decide on what is the end voltage of the Li ion battery and what current gives acceptable light for the Torch. Of course the user may also decide that it is acceptable to have slightly less light output as the battery nears its end voltage (after all, most users are familiar with this behavior in an incandescent torch).

Current Control

The FLASH current is factory set to 1.0 Amp. It can be reduced by turning R25 (10k pot) anticlockwise. The maximum LED current rating is 2 Amps. The FLASH current needs to be adjusted prior to the TORCH current because the FLASH setting affects the TORCH setting but not vice versa.

The TORCH current is factory set at 100mA. It can be reduced by turning R26 (2k pot) anticlockwise.

External Flash LED

An External white LED (or other load) can be connected to the board via J5. This also requires that the on-board LED (D5) be bypassed with J6. Alternatively, a second flash LED (LXCL-PWF1) can be connected in parallel to D5 across J6 (pin 2 is +ve).

AutoTorch/External Torch Mode Control

If J12 is jumpered, then Torch mode will be permanently on (Auto Torch). Alternatively, an external control signal connected to pin 2 of J12 will select Torch mode when Hi (3V – 5V). This logic signal drives the gates of M8, M9, and M10 and must source 0.1mA to develop

3.3V across R36.

Flash PulseTimers/External Flash Pulse Control

There are two on-board 555 timers. One generates the FLASH on-time and the other generates the off-time. The FLASH trigger from these timers is connected to the Current Control circuitry via J8. J8 is jumpered for normal operation. An external triggering circuit can be connected by removing the jumper from J8 and connecting the external signal to pin 1 of J8. There is a 33k pull down resistor on this pin. A logic high signal on this pin will take a FLASH. Make sure that this signal is < 100ms long and does not occur for at least another 2s otherwise the thermal limits of the white LED (D5) will be violated and it will be destroyed.

Auto Flash

If J13 is jumpered then the two 555 timers will be continuously triggered to generate an 80ms flash pulse every 2.5s.

Further Information

CAP-XX will be pleased to provide further information on the applications described here, and on the use of supercapacitors in any application. Please use the contact details on the header page, or visit the cap-XX web site.

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Schematics

LEDpulse

R32

150k

805

Vbat

47k

805

R18 33k

805

Vout

C19 100n

805

FDV302P

SOT23

LSR976

805

SW2

Flash

B3SN

R12

T93YB

500k

ZXT13N50DE6

SOT23-6

1425

C21 100n

805

J13

Auto Flash

1 2

R13

1e6

805

C16 10u

805

C4 10u

805

Manual Boost Disable

1 2

BAT754

SOT23

1 3

C2 10u

805

MBRA130LT3

SMA

D4 BZX84C-4V7

SOT23

1 3

R29 680k

805

Vin

33k

805

1V2

Vbat

C6 10u

805

R4 1k

805

M1 FDC638P

SuperSOT-6

421

R34 3k3

805

Vout

C8 DNP 10u

805

R5 1k

805

C10 DNP 10u

805

C12 100n

805

TC1185

SOT23-A

1 2 3 4

Vin GND *Shdn Bypass

Vout

ZXSC100

SO8

1 2 3 4 5

EM BAS RE VCC Isense

GND

Vdrive

Vin

C3 10u

805

R14 1k

805

*Boost Disable

1V2

R11 47k

805

C11 10u

805

C18 100n

805

LYR976

805

Inductor Current

1 2

R37

150

805

R10 100k

805

R1 82k

805

R8 18k

805

R17

T93YB

R28 220k

805

C7 10u

805

R30

33k

805

TLC556CD

SOIC

1 2 3 4 5 6 7 8

DIS TH CON RES OUT TRIG GND TRIG

OUT

RES

CON

DIS

VCC

Vbat

Offtime Trigger

Undervoltage Lockout Vmin = 3.1V with 350mV Hysteresis

C20 47n

805

U2B

TS1852

OUT

R15 33k

805

R6 3R3

805

C1 GW101

R9 R047

805

FDV302P

SOT23

C9 DNP 10u

805

C13 10u

805

Torch Vout

Vbattery

1 2

33u

ELL6RH

1 2

C5 10u

805

33k

805

GND

1 2

R35

33k

805

R33 33k

805

LM4041

2 1

R16

14k3

805

Vin

C17 100n

805

All information contained herein is strictly confidential APPEB1006 User Manual rev1.0, 31-May-2005 page 5 of 6

Page 6

All information contained herein is strictly confidential APPEB1006 User Manual rev1.0, 31-May-2005 page 6 of 6

R27

1M5

805

R25

T93YB

10k

1V2

Torch Vout

Vout

J11

Torch Voltage

LED Bypass

R21

150

805

U2A

TS1852

OUT

VccVdd

FDV301N

External Timer

R24 33k

805

Offtime Trigger

R26

T93YB

C15

220p

603

R20 33k

805

Pulse Boost Disable

*Boost Disable

R19 100k

805

1V2

R36 33k

805

J10

Torch Boost Disable

SW1

TorchB3SN

ZXM64NO2X

MSOP8

R22 R047

805

FDV301N

R31 33k

805

*Boost Disable

FDV301N

Pulse

R23

3k3

805

Torch/*Flash

GND

LumiLED

M10

FDV301N

J12

Auto Torch

LEDpulse

FDV301N

C14 100n

805

LED Current