LED7708 STMicroelectronics, LED7708 Datasheet - Page 21

• Manufacturer Part Number: LED7708
• Description: LED Lighting Drivers 16 Ch 85mA LED 3.6 to 36V 250kHz
• Manufacturer: STMicroelectronics

Specifications of LED7708

• Rohs: yes

LED7708
8.2
8.3
8.3.1
Device shutdown
The device is turned off by clearing the DEN bit of the DEVCFG0 register. The content of
most of the internal registers is not cleared acting on the DEN bit.
The LREN pin can be also used to turn the device on and off whenever the internal 3.3 V
LDO is used to supply the LED7708 (POR). In this case the content of the internal registers
is lost.
Boost controller section and output voltage control
The boost section of the LED7708 consists of:
●
●
●
●
Output voltage optimization
The output voltage of the boost section is the supply rail for the LED strings and is regulated
in an adaptive way to improve the overall efficiency. A dedicated digital-to-analog converter
(DAC) is used to change the reference voltage of the loop and the output voltage is adjusted
in order to keep the power dissipation of the LED driving section to the minimum level.
The optimization is achieved by keeping the voltage drop across the channels inside a fixed
window (regulation window) and its amplitude can be selected between two values (300 mV
and 600 mV) by acting on the internal registers. The lower threshold of the regulation
window (V
(V
Equation 1
Figure 5
RWH
Fixed-frequency current-mode step-up controller
Output voltage optimization loop
External MOSFET gate driver
Related protection circuitry.
) is therefore determined.
shows the simplified regulation circuit.
RWL
) is a function of the set LED current
Doc ID 022698 Rev 1
V
RWL
=
K
W
⋅
R
ISETH
(Equation
Recommended operating conditions
1) and the upper threshold
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