STEVAL-ISA056V1 STMicroelectronics, STEVAL-ISA056V1 Datasheet - Page 26

• Manufacturer Part Number: STEVAL-ISA056V1
• Description: BOARD EVAL BASED ON PM6600
• Manufacturer: STMicroelectronics
• Type: PWM Controllersr

Specifications of STEVAL-ISA056V1

• Design Resources: STEVAL-ISA056V1 Gerber Files STEVAL-ISA056V1 Schematic STEVAL-ISA056V1 Bill of Material
• Current - Output / Channel: 30mA
• Outputs And Type: 6, Non-Isolated
• Voltage - Output: 36 V
• Features: Dimmable
• Voltage - Input: 4.5 ~ 28V
• Utilized Ic / Part: PM6600
• Input Voltage: 4.5 V to 28 V
• Output Voltage: 36 V
• Product: Power Management Modules
• Core Chip: PM6600
• Topology: Boost
• No. Of Outputs: 1
• Dimming Control Type: PWM
• Mcu Supported Families: PM6600
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PM6600
• Other names: 497-8414

Operation description
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7.1
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Operation description
Boost section
Functional description
The PM6600 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 input voltage range is from 4.7 V up to 28 V.
The boost section is based on a constant switching frequency, Peak Current-Mode
architecture. The boost output voltage is controlled such that the lowest ROWs' voltage,
referred to SGND, is equal to an internal reference voltage (400 mV typ.).
In addition, the PM6600 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 43. AVCC filtering
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 (see
at each ROW according to the set value (RILIM pin).
A dedicated circuit automatically selects the lowest voltage drop among all the ROWs and
provides this voltage the main loop that, in turn, regulates the output voltage. In fact, once
the reference generator has been detected, the error amplifier compares its voltage drop to
the internal reference voltage and varies the COMP output. The voltage at the COMP pin
determines the inductor peak current at each switching cycle. The output voltage of the
boost regulator is thus determined by the total forward voltage of the LEDs strings:
Equation 1
Figure
V
Doc ID 14248 Rev 7
49), while an internal current loop regulates the same current
Cavcc
100n
4R7
Rfilt
OUT
LDO5
AVCC
=
N
max
ROWS
i
=
1
(
m
Σ
LEDS
j
=
1
V
F
LDO
j ,
)
SGND
VIN
+
400
PM6600
mV
PM6600