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
© NXP B.V. 2009. All rights reserved.
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
© NXP B.V. 2009. All rights reserved.
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
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
-
Type
analog IO
analog IO
I
I/O
analog IO
analog I
analog O
ground
analog I
I
O
ground
analog I
input
I
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
© NXP B.V. 2009. All rights reserved.
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
© NXP B.V. 2009. All rights reserved.
Product data sheet
Rev. 05 — 16 December 2009
5 of 26
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