ssl3250a NXP Semiconductors, ssl3250a Datasheet - Page 7

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

NXP Semiconductors
SSL3250A_2
Product data sheet
8.3.1 Shut-down mode
8.3.2 Standby mode
8.3.3 Torch mode
8.3 Operational modes
The external current setting resistor R_FL can still be used in Flash mode but is not
required. When the external current setting resistor R_FL is not used, the pin should
preferably be connected to VIN, this way a default resistor value of approximately 50 k is
assumed. The current setting resistors for the indicator LED, R_IND and for the
Torch mode, R_TR have no function in I
connected to VIN.
The device is in Shut-down mode when the activate pin (ACT) is LOW. In Shut-down
mode the internal circuitry of the device is turned off to guarantee a low shut-down
current. The N-channel MOSFET (NMOS) is set to high-impedance. To limit the LED
current to a minimum leakage, the current sink circuitry for both the main LED and the
indicator LED are switched to high-impedance. After making the pin ACT HIGH, the
device will start up and is ready to receive commands through the selected interface.
In Standby mode the internal circuitry of the device remains on, but the converter is not
switching. The NMOS is set to high-impedance. To limit the LED current to a minimum
leakage, the current sink circuitry for both the main LED and the indicator LED are
switched to high-impedance. In this mode the device is able to respond to I
communication.
The Torch mode allows the main LED to be switched on, without timing limitations, at a
lower LED current setting. The Torch mode current in the main LED can be set between
50 mA and 200 mA in both the I
In I
a maximum of 11 in the current control register. In I
ignored. If an external R_FL resistor is connected, this resistor will also scale down the set
torch current. See
using
equation. Entering Torch mode is done by writing the required current setting in the
current control register. The LED will light to the set torch current. Switching off the Torch
mode can be done by writing 0h into the current control register, or by entering Flash
mode, see
When using the Direct enable mode, the torch current is defined by an external resistor
connected to the R_TR pin. The LED current is defined using
the current set resistor, the torch current will be set to a default level of 125 mA. The
I
2. Trigger the Flash mode either by the hardware STRB pin or by the FLASH_STRB bit
LED
2
in the Flash strobe register 02h. When the external strobe pin is not used it should be
connected to GND to prevent false strobing of the main LED.
C mode, the LED current is defined by entering a value between a minimum of 1 and
=
Equation
50 k
---------------
R
R_FL
Section
1. When not using the resistor R_FL, assume a value of 50 k in the
+
Section
35 mA
8.3.4.
Rev. 02 — 21 April 2009
+
8.3.6. The current in the main LED using I
15 mA
2
C and Direct enable control mode.
Register
2
C mode and the pins should preferably be
2
C mode the external R_TR resistor is
Photo flash dual LED driver
Equation
SSL3250A
2
C mode is defined
2. When not using
© NXP B.V. 2009. All rights reserved.
2
C
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