ssl3250a NXP Semiconductors, ssl3250a Datasheet - Page 5

• Manufacturer Part Number: ssl3250a
• Description: Photo ?ash Dual Led Driver
• Manufacturer: NXP Semiconductors

NXP Semiconductors
8. Functional description
SSL3250A_2
Product data sheet
8.1 Introduction
8.2 Interface modes
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
lines. Both interface modes control the five operational modes. These operational modes
are:
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
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).
The device is equipped I
mode is used, is defined by the level of the IF_SEL pin at the start-up of the device
(V
up the device.
Table 4.
IF_SEL
0
1
•
•
•
•
•
ACT
Shut-down mode
Standby mode
Indicator mode
Torch mode
Flash mode
LOW to HIGH). The state of the IF_SEL pin should be kept static after powering
Interface modes
Interface mode
I
Direct enable mode
2
C mode
Table 4
shows the interface possibilities.
Rev. 02 — 21 April 2009
2
C mode and Direct enable mode interfaces. Which interface
2
C interface mode is enabled, the operational modes
Relevant controls
SDA, SCL, STRB, ACT, R_FL, INT.
EN1, EN2, ACT, INT, R_TR, R_FL, R_IND, INT.
2
C interface or by external enable
Photo flash dual LED driver
SSL3250A
© NXP B.V. 2009. All rights reserved.
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