STMicroelectronics STLDC08 Demo Board STEVAL-ILL039V1/2 STEVAL-ILL039V1 STEVAL-ILL039V1 データシート
製品コード
STEVAL-ILL039V1
Detailed description
STLDC08
14/29
Doc ID 18476 Rev 1
7.3
Over voltage protection (OVP)
As with any current source, the output voltage rises when the output gets high impedance or
is disconnected. To prevent the output voltage exceeding the maximum switch voltage rating
of the main switch, an overvoltage protection circuit is integrated. As soon as the output
voltage exceeds the OVP threshold, the converter stops switching and the output voltage
drops. When the output voltage falls below the OVP threshold, the converter continues
operation until the output voltage exceeds the OVP threshold again.
is disconnected. To prevent the output voltage exceeding the maximum switch voltage rating
of the main switch, an overvoltage protection circuit is integrated. As soon as the output
voltage exceeds the OVP threshold, the converter stops switching and the output voltage
drops. When the output voltage falls below the OVP threshold, the converter continues
operation until the output voltage exceeds the OVP threshold again.
7.4 Enable/PWM
The enable pin allows disabling and enabling of the device as well as brightness control of
the LEDs by applying a PWM signal. In order to avoid visible flicker, the frequency of the
PWM signal should be higher than 120 Hz. Changing the PWM duty cycle therefore
changes the LED brightness.
the LEDs by applying a PWM signal. In order to avoid visible flicker, the frequency of the
PWM signal should be higher than 120 Hz. Changing the PWM duty cycle therefore
changes the LED brightness.
Figure 17.
Timing diagram
V
CC
2VCC
DRV
PWMOUT
V
OUT
I
CC
ILED
Charge Pump
active
STLDC08 supplied by
V
OUT
V
OUT
> V
LED
, the current starts
flowing through the LEDs
V
OUT
>1.9 V STLDC08 is
supplied by V
OUT
Follows EN/PWM
input
input
Soft start cycle ended,
PWMOUT is realeased
1.7 V
1.9 V
AM07847v1
V
CC
2VCC
DRV
PWMOUT
V
OUT
I
CC
ILED
Charge Pump
active
STLDC08 supplied by
V
OUT
V
OUT
> V
LED
, the current starts
flowing through the LEDs
V
OUT
>1.9 V STLDC08 is
supplied by V
OUT
Follows EN/PWM
input
input
Soft start cycle ended,
PWMOUT is realeased
1.7 V
1.9 V
AM07847v1