LED7707 STMicroelectronics, LED7707 Datasheet - Page 11

• Manufacturer Part Number: LED7707
• Description: LED Drivers 6-ROW 85mA LED DRIV BOOST REG LCD PANEL
• Manufacturer: STMicroelectronics

Specifications of LED7707

• High Level Output Current: 85 mA
• Operating Supply Voltage: 4.5 V to 36 V
• Maximum Supply Current: 1 mA
• Maximum Power Dissipation: 2.3 W
• Maximum Operating Temperature: + 150 C
• Mounting Style: SMD/SMT
• Package / Case: VFQFPN-24
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LED7707
5.1
5.1.1
Boost section
Functional description
The LED7707 is a monolithic LEDs driver for the backlight of LCD panels and it consists of a
boost converter and six PWM-dimmable current generators.
The boost section is based on a constant switching frequency, peak current-mode
architecture. The boost output voltage is controlled such that the lowest row's voltage,
referred to SGND, is equal to an internal reference voltage (700 mV typ.). The input voltage
range is from 4.5 V up to 36 V. In addition, the LED7707 has an internal LDO that supplies
the internal circuitry of the device and is capable to deliver up to 40 mA. The input of the
LDO is the VIN pin.
The LDO5 pin is the LDO output and the supply for the power MOSFET driver at the same
time. The AVCC pin is the supply for the analog circuitry and should be connected to the
LDO output through a simple RC filter in order to improve the noise rejection.
Figure 4.
Two loops are involved in regulating the current sunk by the generators.
The main loop is related to the boost regulator and uses a constant frequency peak current-
mode architecture to regulate the power rail that supplies the LEDs
internal current loop regulates the same current (flowing through the LEDs) at each row
according to the set value (RILIM pin).
Figure 5.
AVCC filtering
Main loop and current loop diagram
COMP
Slope
V
IN
Error amplifier
E/A
PWM
LX
0.7V
Minimum voltage drop
selector
(Figure
Operation description
5), while an
ROWx
RILIM
SGND
AM00582v1
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