AS3645 austriamicrosystems, AS3645 Datasheet - Page 10

• Manufacturer Part Number: AS3645
• Description: 1000/720ma Ultra Small High Efficient Single/dual Led Flash Driver With Safety Features
• Manufacturer: austriamicrosystems

AS3645
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS3645 is a high performance DCDC step up converter with internal PMOS and NMOS switches. Its output is
connected to a flash LED
LED.
The AS3645 can be operated in the following modes:
The advantage of the parallel interface mode is the simple control of the AS3645 whereas the I
adjusting of all the currents and operating functions.
Internal Circuit
The AS3645 includes a fixed frequency DCDC step-up with accurate startup control. Together with the two output cur-
rent sources (on LED_OUT or IND_OUT) it includes several protection and safety functions as shown in the following
internal blockdiagram:
Figure 16. AS3645 internal circuit
The DCDC converter always operates in PWM mode (exception: PFM mode is allowed during startup until single/dual
LED detection is done.
www.austriamicrosystems.com
1. A single or dual flash LEDs connected in series is supported.
1. I
2. parallel interface mode with fixed output currents (500mA flash current for a single LED, 320mA flash current
3. parallel interface mode with adjustable output currents - selected by connecting a resistor (R
achieved in this operating mode only) - selected with I2C/EN=H
for two flash LEDs) - selected with I2C/EN=L
EN. All flash LED currents (pin LED_OUT) can be adjusted with this resistor (max 500mA flash current for a
single LED, max 320mA flash current for two flash LED).
2
C mode with full control of all the current settings (the maximum flash current of up to 1000mA can be
See Single/Dual LED Detection on page
1
with an internal current source. A separate current source is used to connect an indicator
AS3645
Revision 1.6
12) to reduce EMI in EMI sensitive systems.
2
C mode allows for
ISET
) on pin I2C/
10 - 33