STEVAL-ILL021V1 STMicroelectronics, STEVAL-ILL021V1 Datasheet - Page 11
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STEVAL-ILL021V1
Manufacturer Part Number
STEVAL-ILL021V1
Description
BOARD EVAL LCD BACKLIGHT LED7707
Manufacturer
STMicroelectronics
Specifications of STEVAL-ILL021V1
Design Resources
STEVAL-ILL021V1 Bill of Material STEVAL-ILL021V1 Schematic
Current - Output / Channel
85mA
Outputs And Type
6, Non-Isolated
Voltage - Output
36 V
Features
Dimmable, Extra 5V Output
Voltage - Input
4.5 ~ 36 V
Utilized Ic / Part
LED7707
Description/function
LCD backlight demonstration board
Operating Voltage
4.5 V to 36 V
Product
Display Modules
Core Chip
LED7707
No. Of Outputs
1
Output Voltage
36V
Dimming Control Type
PWM
Mcu Supported Families
LED7707
Lead Free Status / RoHS Status
Lead free by exemption / RoHS compliant by exemption
For Use With/related Products
LED7707
Other names
497-10044
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
STEVAL-ILL021V1
Manufacturer:
STMicroelectronics
Quantity:
1
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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