AS3644 Datasheet, PDF (21/24 Pages) ams AG – Ultra Small Low Cost 320mA Inductive White LED Flash Driver

AS3644
Datasheet - Application Information
Application Self Testing Guideline
Using the in-build self testing features of the AS3644, the errors as shown in Figure 24 during the assembling and sol-
dering of the AS3644, can be detected - this simplifies and can reduce cost during manufacturing:
Figure 24. Self Testing - Detecting Assembling and Soldering Errors

 

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ill ^v
t 
AS3644
 
G _{s The self testing procedure is simple:}
A ^t _{1. Write 0x20 into register 0x03 (Control register) [Enable assist light with default 72mA].}
s ^{n 2. Read back4 register 0x03 - must return 0x20, otherwise LDCDC or I2C (SCL or SDA) is broken}
3. Write 0x00 into register 0x03 [Power off]
e _{4. Read register 0x04 (Fault register) - must return 0x00, otherwise the LED is open or shorted}
m ^t _{See Table 14to identify the different possible soldering errors:}
a ⁿ _{Table 14. How-to identify errors}
o _Error
Identified by
c SCL or SDA broken
writing 0x20 to 0x03 and read back of register 0x03 does not return 0x20
l ^{LDCDC broken}
writing 0x20 to 0x03 and read back of register 0x03 does not return 0x20 - see DCDC
Broken Coil Detection on page 11
a ^{Flash LED shorted}
register fault_led_short (see page 17) is set
Technic ^{Flash LED open}
register fault_ovp (see page 17) is set
4. Alternative testing method: Instead of reading the internal registers, the current into the AS3644 can be
measured. During assist light mode, the supply current must increase by at least 60mA. If an error is
detected, the current source and the DCDC is automatically switched off - see Protection and Fault Detec-
tion Functions on page 10
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