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SSL3250A

Photo flash dual LED driver

Rev. 05 — 16 December 2009

Product data sheet

1. General description

The SSL3250A is a photo flash LED driver designed for battery operated mobile devices

such as mobile phones and PDAs. The boost converter delivers high performance and

drives a single or dual, high brightness LED at up to 500 mA with over 85 % efficiency.

The driver can be programmed to operate in Flash, Torch or Indicator / Video-on mode.

The small silicon size and the high internal switching frequency of 1.2 MHz minimize the

SSL3250A footprint making it very suitable for mobile phones where space is limited, and

only requiring four external components. Driving a high power flash LED within its safe

operating limits was a concern when the SSL3250A was designed, so a time-out function

can be programmed via the I

2

C interface, which will prevent overstressing the LED. Due

to the specific requirements of a mobile phone, the flash current can be rapidly lowered

during RF transmit by using optional external setting resistors.

2. Features

High power single, or dual, LED output driving up to 500 mA flash current

Separate indicator LED output of 2.5 mA to 20 mA

Output voltage of up to 9.5 V

Wide input voltage range of 2.7 V to 5.5 V

High efficiency, over 85 % at optimum output current

Switching frequency of 1.2 MHz

Flash, Torch, and Indicator mode supported

Internally timed flash operation up to 820 ms

I

2

C-bus, programmable up to 400 kHz

Strobe signal to avoid I

2

C latency for flash

Discrete enable signals for stand-alone operation

Optional resistor configurable output currents

Fast response to accommodate external TxMasking functionality

Soft start in Torch and Flash modes to avoid battery overloading

Integrated protection circuits for enhanced system reliability

Internal time-out function

OverTemperature Protection (OTP)

UnderVoltage LockOut (UVLO)

OverVoltage Protection (OVP)

Output current protection

Interrupt signaling to system controller

Low device shut-down current, less than 1

μA

SOT758-3, thermally enhanced 16 terminal HVQFN package

NXP Semiconductors

SSL3250A

Photo flash dual LED driver

3. Applications

White LED driver for battery powered portable devices

Photo flash LED driver for mobile phones and digital cameras

4. Ordering information

Table 1.

Ordering information

Package

Name

SSL3250AHN/C1 HVQFN16

Description

Version

plastic thermal enhanced very thin quad flat package; SOT758-3

no leads; 16 terminals; body 3

×

3

×

0.85 mm

Type number

4.1 Ordering options

Table 2.

Ordering options

Orderable part number

SSL3250AHN/C1,528

Pin 1 indicator location for tape and reel

Pin 1 in quadrant 2. See

Figure 1.

Type number

SSL3250AHN/C1

5. Marking

pin 1 indicator

direction of unreeling

002aae613

Fig 1.

SSL3250AHN/C1,528 with package rotated 90° clockwise with pin 1 in quadrant 2

SSL3250A_5

Product data sheet

Rev. 05 — 16 December 2009

2 of 26

NXP Semiconductors

SSL3250A

Photo flash dual LED driver

6. Block diagram

V

BAT

4.7

μF

Ceramic

2.2

μH

PGND

VIN

INTERNAL

SUPPLY

I_IND

LX

SSL3250A

VO

IF_SEL

SDA/EN1

SCL/EN2

STRB

INT

ACT

PGND

R_IND

R_FL

R_TR

I

2

C INTERFACE

AND CONTROL

LINEAR

CURRENT SINK

CURRENT

FEEDBACK

UP CONVERTER

4.7

μF

Ceramic

PGND

One or two LEDs

LED

Isink

R1

R2

R3

GND

PGND

GND

014aaa286

Fig 2.

Block diagram

SSL3250A_5

Product data sheet

Rev. 05 — 16 December 2009

3 of 26

NXP Semiconductors

SSL3250A

Photo flash dual LED driver

7. Pinning information

7.1 Pinning

15 ACT

terminal 1

index area

16 STRB

14 VIN

R_TR

R_FL

SCL/EN2

SDA/EN1

1

2

13 LX

12 PGND

11 INT

10 IF_SEL

9 LED

GND

014aaa363

SSL3250A

3

4

5

6

7

VO

8

R_IND

Transparent top view

Fig 3.

Pin configuration (terminal 1 index area is die pad GND)

7.2 Pin description

Table 3.

Symbol

R_TR

R_FL

SCL / EN2

SDA / EN1

R_IND

I_IND

VO

GND

LED

IF_SEL

INT

PGND

LX

VIN

ACT

STRB

die pad

Pin description

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

-

Type

analog IO

I

I/O

analog IO

analog I

analog O

ground

analog I

I

O

ground

analog I

input

I

analog

Description

setting resistor for torch current

setting resistor for flash current

Serial Clock Line (SCL) in I

2

C mode / Enable 2 in Direct enable

mode

Serial Data Line (SDL) in I

2

C mode / Enable 1 in Direct enable

mode

setting resistor for indicator current

indicator LED current sink

output voltage

ground

feedback of the main LED current

interface select; choose between direct enable control or I

2

C

interrupt output (open collector)

power ground

inductor connection

input voltage

activate

strobe signal to enable flash in I

2

C mode

exposed die pad; connect to GND

SSL3250A_5

I_IND

Product data sheet

Rev. 05 — 16 December 2009

4 of 26

NXP Semiconductors

SSL3250A

Photo flash dual LED driver

8. Functional description

8.1 Introduction

The SSL3250A is an asynchronous boost converter intended to drive either a single high

power flash LED or two high power flash LEDs in series. The main LED current is

controlled by the output voltage of the boost converter and the integrated linear current

sink. The SSL3250A has two interface modes and five operational modes. The control

interface is selected by the interface select pin IF_SEL. Depending on the interface mode

selected, the device can either be controlled by an I

2

C interface or by external enable

lines. Both interface modes control the five operational modes. These operational modes

are:

•

Shut-down mode

Standby mode

Indicator mode

Torch mode

Flash mode

The first mode is entered by putting a LOW level on the activate pin (ACT). This pin is

common for both interface modes. The operational modes Torch and Flash apply to the

same main LED current source, and the Indicator mode applies to a separate indicator

LED current source. Only when the I

2

C interface mode is enabled, the operational modes

Indicator, Flash and/or Torch can be used in parallel.

In normal operation, the regulated converter uses Pulse Width Modulation (PWM), so the

switching frequency is constant in all modes.

In applications where the required main LED voltage is lower than the applied input

voltage, the converter switches to linear mode. The excess voltage difference between

the required LED voltage and the input voltage is now compensated by increasing the

voltage over the current sink and therefore on the LED pin.

Apart from the main LED(s), a separate indicator LED can be driven from the SSL3250A.

This indicator LED is driven by a linear current sink circuit that operates independently

from the switch mode converter for the main LED(s).

8.2 Interface modes

The device is equipped I

2

C mode and Direct enable mode interfaces. Which interface

mode is used, is defined by the level of the IF_SEL pin at the start-up of the device

(V

ACT

→

LOW to HIGH). The state of the IF_SEL pin should be kept static after powering

up the device.

Table 4

shows the interface possibilities.

Table 4.

IF_SEL

0

1

Interface modes

Interface mode

I

2

C mode

Direct enable mode

Relevant controls

SDA, SCL, STRB, ACT, R_FL, INT.

EN1, EN2, ACT, INT, R_TR, R_FL, R_IND, INT.

SSL3250A_5

Product data sheet

Rev. 05 — 16 December 2009

5 of 26

SSL3250A_0912

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