PM6600 STMicroelectronics, PM6600 Datasheet - Page 49

• Manufacturer Part Number: PM6600
• Description: IC LED DRIVR WHT BCKLT 24-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Backlight, White LEDr

Specifications of PM6600

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 200kHz ~ 1MHz
• Voltage - Supply: 4.7 V ~ 28 V
• Voltage - Output: 36V
• Mounting Type: Surface Mount
• Package / Case: 24-VFQFN, 24-VFQFPN
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 32mA
• Internal Switch(s): Yes
• Number Of Segments: 60
• Operating Supply Voltage: 4.7 V to 28 V
• Maximum Power Dissipation: 2.3 W
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• For Use With: 497-8414 - BOARD EVAL BASED ON PM6600
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Efficiency: -
• Lead Free Status / Rohs Status: Details

PM6600
B.4
B.4.1
B.4.2
B.4.3
Design example
In order to help the design of an application using the PM6600, in this section a simple step-
by-step design example is provided.
A typical application could be the LCD backlight in a 14.1” LCD panel using the PM6600.
Here below the possible application conditions are listed:
●
●
●
Switching frequency setting
To reduce the number of the external components, the default switching frequency is
selected (660 kHz typ.) by connecting the FSW pin to AVCC pin.
However, in case a different switching frequency is required, a resistor from FSW pin and
ground can be connected, according to the equation
Equation 22
Row current setting
The ROWs current is set using a resistor connected to the RILIM pin of the device. The
R
Equation 23
Inductor choice
The boost section, as all DC-DC converters, can work in CCM (continuous conduction
mode) or in DCM (discontinuous conduction mode) depending on load current, input and
output voltage and other parameters, among which the inductor value.
In a boost converter it is usually preferable to work in DCM.
Once the load, the input and output voltage, and the switching frequency are fixed, the
inductor value defining the boundary between DCM and CCM operation can be calculated
as:
Equation 24
where D is the duty-cycle defined as:
RILIM
V
6 ROWs x 8 WLEDs @ 20 mA
V
IN
F, LEDs
resistor can be calculated as:
= 12 ± 20%
= 3.5 V ± 200 mV
R
RILIM
Doc ID 14248 Rev 7
=
L
I
B
ROW
K
=
R
R
FSW
R
=
0
⋅
998
2
20
D
=
⋅
⋅
F
F
2
(
1
SW
SW
mA
5 .
−
V
D
)
=
2
49
.
k 9
Ω
Application note
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