PM6600 STMicroelectronics, PM6600 Datasheet - Page 32

• 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

Operation description
7.4.2
32/60
Figure 48. Load transient response measurement set-up
Slope compensation
The constant frequency, peak current-mode topology has the advantage of very easy loop
compensation with output ceramic capacitors (reduced cost and size of the application) and
fast transient response. In addition, the intrinsic peak-current measurement simplifies the
current limit protection, avoiding undesired saturation of the inductor.
On the other side, this topology has a drawback: there is inherent open loop instability when
operating with a duty-ratio greater than 0.5. This phenomenon is known as “sub-harmonic
instability” and can be avoided by adding an external ramp to the one coming from the
sensed current. This compensating technique, based on the additional ramp, is called
“Slope Compensation”. In figure 11, where the switching duty-cycle is higher than 0.5, the
small perturbation ΔIL dies away in subsequent cycles thanks to the slope compensation
and the system reverts to a stable situation.
Figure 49. Main loop and current loop diagram
V
IN
= 6V
+5V
C
IN
COMP
LDO5
BILIM
RILIM
SS
COMP
SGND
V
6.8μH
IN
PM6600
Doc ID 14248 Rev 7
ROW1
ROW2
ROW3
ROW4
ROW5
ROW6
g
PWM
m
LX
0.4V
Up to 10 WLEDs per row
Minimum voltage drop
4.7μF
MLCC
V
BST=30÷36V
selector
ROWx
R
PM6600
L
500Hz
RILIM
SGND
=
50mA
V
BST