AS3693B

austriami crosyst ems

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Revision 1.21 / 2011-09-30

18 - 32

Table 20– Curreg1-16_HT_MSB

Addr: 13h-31h

CURREGX_HT_MSB

Defines High Time of PWM

Bit

Bit Name

Default

Access

Description

3:0

Curreg1_HT_MSB

0000

R/W

Defines PWM high time

7.5 Shunt Regulator

The supply of the AS3693B is generated from the high voltage supply. To obtain a 5V regulated supply, a series

resistor Rvdd is used together with an internal zener diode (ZD1). An external capacitor Cvdd is used to filter the

supply on the pin VREG.

The external resistor Rvdd has to be choosen according to the following formula:

possible to supply the AS3693B directly. In this case remove the resistor Rvdd and connected this supply

directly to VREG.

7.5.1 Undervoltage lockout

The undervoltage lockout is an additional safety feature to prevent LED-current under abnormal Vreg conditions.

If the supply voltage Vreg is below 2.7V (e.g. device is supplied only by the voltage of the serial interface ) the

registers Reg.Control1 and RegControl2 (0x01 and 0x02) are reset. This turns off all current sinks.

Vreg

2.7V

Register 0x01

Reset

Register 0x02

Reset

3V to 5.4V

7.6 Over temperature control

Table 14– Overtemp Control

Addr:55h

Over temperature Control

Controls the temperature functions

Bit

Bit Name

Default

Access

Description

0

overtemp_on

1

R/W

Enables the over temperature protection

0 = Protection off

1 = Protection on

1

ov_temp

0

R/W

Displays temperature status

0 = Normal operation

1 = Over temperature shutdown

mA

V

VDD

Rvdd

MIN

20

4

,

5

−

=

supply, where Rvdd is connected