SSL3252
Photo flash LED driver
Rev. 1 — 7 July 2011
Product data sheet
1. General description
The SSL3252 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 mode, Torch mode, Assist light mode, or
Indicator mode.
The small silicon size and the high internal switching frequency of 2 MHz minimize the
size of the application and make the SSL3252 very suitable for mobile phones where
space is limited, and only requiring three external components. System protection has
been a very important part of the SSL3252 design, so a time-out function can be
programmed to prevent overstressing the LED, and the driver itself is protected from
overheating.
2. Features and benefits
High power single or dual LED output driving up to 500 mA flash current
Separate indicator LED output of 2.5 mA to 10 mA
High side current source for main and indicator LEDs
Output voltage of up to 8.85 V
Wide input voltage ranging from 2.5 V to 5.5 V
High efficiency of over 85 % at optimum output current
Switching frequency of 2 MHz
Flash mode, Assist light mode, Torch mode and Indicator mode are supported
Internally timed flash operation up to 850 ms
I
2
C-bus, programmable up to 400 kHz
Strobe signal to avoid I
2
C latency for the flash
Direct enable signals for stand-alone operation
Forward voltage sensing to allow single/dual LED detection
Soft start/soft stop
Integrated protection circuits for enhanced system reliability:
Internal time-out
OverTemperature Protection (OTP)
UnderVoltage LockOut (UVLO)
OverVoltage Protection (OVP)
Short-circuit protection
Inductor peak current limit and broken coil detection
Low device shut-down current of less than 1
A
Small WLCSP12 package with 500
m
bump pitch
NXP Semiconductors
SSL3252
Photo flash LED driver
3. Applications
Photo flash LED driver for mobile phones and digital cameras
White LED driver for battery powered portable devices
4. Ordering information
Table 1.
Ordering information
Package
Name
SSL3252UK/C2
WLCSP12
Description
wafer level chip-size package; 12 bumps; 1.58
2.06
0.6 mm
Version
SSL3252UK
Type number
5. Block diagram
V
BAT
2.2 µH
4.7 µF
PGND
VIN
LX
VO
4.7 µF
IF_SEL
SDA/EN2
SCL/EN1
STRB/2LED
TORCH
I
2
C-BUS
INTERFACE
AND CONTROL
400 kHz
LINEAR
CURRENT
SOURCE
CURRENT
FEEDBACK
SYNCHRONOUS
SWITCHER
UP CONVERTER
PGND
I
source
LED one or two LEDs
R1
R2
(1)
R3
(2)
R4
(2)
I_IND
GND
GND
PGND
PGND
014aaa297
(1) Pull-down resistor R2 is connected to STRB/2LED pin only in I
2
C mode.
(2) Pull-down resistors R3 and R4 are connected to the EN1 and EN2 functions of the SCL/EN1 and SDA/EN2 pins only in Direct
enable mode.
Fig 1.
Block diagram
SSL3252
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 1 — 7 July 2011
2 of 30
NXP Semiconductors
SSL3252
Photo flash LED driver
6. Pinning information
6.1 Pinning
Bump A1
Index area
A
B
C
D
Transparent top view
002aag318
SSL3252UK/C2
1
2
3
Fig 2.
Pin configuration
6.2 Pin description
Table 2.
Symbol
PGND
GND
VIN
LX
TORCH
I_IND
VO
STRB/2LED
IF_SEL
LED
SDA/EN2
SCL/EN1
Pin description
Pin
A1
A2
A3
B1
B2
B3
C1
C2
C3
D1
D2
D3
Type
ground
ground
input
analog input
input
analog output
analog output
input/output (I/O)
input
analog output
input/output (I/O)
input
Description
power ground
signal ground
input voltage
inductor connection
Torch mode activate
indicator LED current source
output voltage
strobe signal input to trigger flash in I
2
C mode;
2LED signal output in Direct enable mode (open-drain)
interface select; choose between Direct enable mode
or I
2
C mode
main LED current source
serial data line in I
2
C mode / enable 2 in Direct enable
mode
serial clock line in I
2
C mode / enable 1 in Direct enable
mode.
SSL3252
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 1 — 7 July 2011
3 of 30
NXP Semiconductors
SSL3252
Photo flash LED driver
7. Functional description
7.1 Introduction
The SSL3252 is a boost converter intended to drive either a single high power flash LED
or two high power flash LEDs in series. The LED current is controlled by the output
voltage of the boost converter and the integrated linear current source. The SSL3252 has
two interface modes and six operational modes. The interface mode 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-bus interface, or external enable lines.
The interface modes are:
•
I
2
C mode
•
Direct enable mode
The operational modes are:
•
•
•
•
•
•
Standby mode
Shut-down mode
Flash mode
Torch mode
Assist light mode
Indicator mode
In all LED modes, to ensure a constant switching frequency, the regulated converter
employs Pulse Width Modulation (PWM).
In applications where the required 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 input voltage is now compensated by increasing the voltage over the
linear current source and therefore on the LED pin.
Apart from the main LED(s), a separate indicator LED can be driven from the SSL3252.
This is driven by a linear current source circuit that operates independent of the switch
mode converter for the main LED(s).
7.2 Interface modes
The device is equipped with two interfaces: I
2
C and Direct enable. Which interface mode
is used is defined by the level of the IF_SEL pin.
Table 3
describes the interface
possibilities.
Table 3.
IF_SEL
1
0
Interface modes
Interface mode
I
2
C mode
Direct enable mode
Relevant controls
SDA, SCL, STRB/2LED, TORCH
EN1, EN2, TORCH
SSL3252
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 1 — 7 July 2011
4 of 30
NXP Semiconductors
SSL3252
Photo flash LED driver
7.2.1 Using the direct enable control
When the Direct enable mode is used, the device can be switched to the various
operational modes using the TORCH, EN1 and EN2 control signals. The definitions of
these control signals are given in
Table 4.
The EN1 and EN2 functions of the SCL/EN1
and SDA/EN2 pins have a higher priority than the pin TORCH.
Figure 3
shows all the
possible transitions between the various interface modes.
The device is in Shut-down mode when all control pins (IF_SEL, EN1, EN2, TORCH) are
LOW.
Shut-down
mode
Indicator
mode
Torch
mode
Flash
mode
Assist light
mode
014aaa303
Fig 3.
Table 4.
Direct enable mode transitions
Direct enable logic definition
Output states
IF_SEL SCL/ SDA/ TORCH Mode
pin
EN1 EN2 pin
pin
pin
0
0
0
0
0
[1]
0
0
0
1
1
0
0
1
0
1
0
1
X
[1]
X
[1]
X
[1]
Shut-down
Torch
Assist light
Indicator
Flash
Outputs disabled; shut-down current less than
1
A
Fixed value; 40 mA dual LEDs; 80 mA single LED
Fixed value; 40 mA dual LEDs; 80 mA single LED
Fixed value 2.5 mA
Fixed value; 320 mA dual LEDs;
500 mA single LED
X = Don’t care.
SSL3252
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 1 — 7 July 2011
5 of 30
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