PM6600 STMicroelectronics, PM6600 Datasheet - Page 27

• 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
7.2
where the first term represents the highest total forward voltage drop over active ROWs and
the second is the voltage drop across the leading generator (400 mV typ.).
The device continues to monitor the voltage drop across all the rows and automatically
switches to the current generator having the lowest voltage drop.
Overvoltage protection
An adjustable over-voltage protection is available. It can be set feeding the OVSEL pin with a
partition of the output voltage. The voltage of the central tap of the divider is thus compared
to a fixed 1.235 V threshold. When the voltage on the OVSEL pin exceeds the OV threshold,
the FAULT pin is tied low (see
condition is latched and the PM6600 is restarted by toggling the EN pin or by performing a
power-on reset (the POR occurs when the LDO output falls below the lower UVLO threshold
and subsequently crosses the upper UVLO threshold during the rising phase of the input
voltage). Normally, the value of the high-side resistors of the divider is in the order of 100k Ω
to reduce the output capacitor discharge when the boost converter is off (during the off
phase of the dimming cycle).
The OVSEL divider should be a compensated one, with the capacitors C10 (typically in the
100 pF-330 pF range) that improves noise rejection at the OVSEL pin (see
C13 (typically 22 pF) that avoids OVP fault detection when a row is open.
The following formulas permit to properly select the OVP threshold, according to the VOUT
value and considering the worst case (maximum VF_WLED):
Equation 2
Equation 3
V
V
The formula to choose the proper values for the resistors of the OVP divider is:
Equation 4
Equation 5
OUTmax
OVP
is the over-voltage protection threshold
is the maximum output voltage considering the LED spread.
V
OUT
max
V
OUT
Section 9 on page 39
Doc ID 14248 Rev 7
+
max
3
V
=
<
R
C
n
WLED
1
V
13
OVP
=
=
_
R
series
1.5 C
2
<
⎛
⎝
----------------------- -
1.235 1
V
⋅
VOVP
OUT
⋅
V
10
F
_
WLED
–
⋅
+
) and the device is turned off; this
R
------ -
R
V
⎞
⎠
2
1
OUT
max
max
+
0
4 .
+
V
4
5 .
) V
Operation description
Figure 44
) and
27/60