LED7706 STMicroelectronics, LED7706 Datasheet - Page 34

• Manufacturer Part Number: LED7706
• Description: IC LED DRIVR WHT BCKLT 24-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Backlight, White LEDr

Specifications of LED7706

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 250kHz ~ 1MHz
• Voltage - Supply: 4.5 V ~ 36 V
• Voltage - Output: 36V
• Mounting Type: Surface Mount
• Package / Case: 24-VFQFN, 24-VFQFPN
• Current - Output / Channel: 30mA
• Internal Switch(s): Yes
• Operating Supply Voltage: 4.5 V to 36 V
• Maximum Supply Current: 1 mA
• Maximum Power Dissipation: 2300 mW
• Maximum Operating Temperature: + 150 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• For Use With: 497-10043 - BOARD EVAL LCD BACKLIGHT LED7706497-8360 - BOARD EVAL FOR LED7707497-6445 - EVALUATION BOARD FOR LED7706
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Operating Temperature: -
• Efficiency: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Application information
6.4.7
6.4.8
34/46
Equation 40
R
the resistor divider. For example, setting R
standard commercial value is R
The correct selection of the OVP divider (and, as consequence, the open channel detection
threshold) must take into account the shorted LED fault threshold (see
When the selected OVP threshold is too high, an undesired triggering of the shorted LED
detection circuitry may occur when a channel opens.
In fact, as explained in section 4.3.3, once a channel opens, the device reacts increasing the
output voltage and the voltage across the working current generators may reach the shorted
LED detection threshold before the open channel detection threshold.
Compensation network
For the compensation network, the suggestions provided in
In this condition, tentatively the following value of R3 and C8 (see
good choice for the loop stability:
R
C
Boost current limit
The boost current limit is set to protect the internal power switch against excessive current.
The slope compensation may reduce the programmed current limit. Hence, to take into
account this effect, as a rule of thumb, the current limit can be set as twice as much the
maximum inductor peak current (see
I
Therefore, using equation (8) and choosing I
Equation 41
BOOST, PEAK
1
3
8
can be chosen is in the order of hundreds of kilo-ohms to reduce the leakage current in
= 2.4 kΩ
= 4.7 nF
> 2.09 A
V
OUT
,
OVP
R
2
BILIM
= 22 kΩ.
=
nLED
Section 6.4.4
=
I
BOOST
1
⋅
V
= 510 kΩ leads to R
K
BOOST, PEAK
, F
B
,
PEAK
max
+
):
=
400
240
mV
= 2.5 A, R
k
Ω
=
Section 6.1
30
2
V
= 21.89 kΩ. The closest
Figure 23
BILIM
Section 5.3.4
are always valid.
will be:
) are usually a
LED7706
).