EVALED7706 STMicroelectronics, EVALED7706 Datasheet - Page 11

• Manufacturer Part Number: EVALED7706
• Description: EVALUATION BOARD FOR LED7706
• Manufacturer: STMicroelectronics

Specifications of EVALED7706

• Current - Output / Channel: 30mA
• Outputs And Type: 6, Non-Isolated
• Voltage - Output: 36 V
• Features: Dimmable, Extra 5V Output
• Voltage - Input: 4.5 ~ 36 V
• Utilized Ic / Part: LED7706
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6445

LED7706
5.1
5.1.1
Boost section
Functional description
The LED7706 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 (400 mV typ. see
input voltage range is from 4.5 V up to 36 V. In addition, the LED7706 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
C
C
V
IN
1uF
1uF
LDO5
LDO5
C
C
100nF
100nF
Rfilt
Rfilt
4R7
4R7
AVCC
AVCC
Error amplifier
LDO5
LDO5
AVCC
AVCC
E/A
PWM
LX
0.4V
LDO
LDO
SGND
SGND
VIN
VIN
Minimum voltage drop
LED7706
LED7706
selector
(Figure
Operation description
5), while an
ROWx
Figure
SGND
RILIM
5). The
AM00597v1
AM00598v1
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