ISL97682IRTZ-TK Intersil, ISL97682IRTZ-TK Datasheet - Page 11

• Manufacturer Part Number: ISL97682IRTZ-TK
• Description: 2 Channel LED Driver, 16LD TQFN 3X3, 1K T&R
• Manufacturer: Intersil
• Series: -r

Specifications of ISL97682IRTZ-TK

• Constant Current: -
• Constant Voltage: -
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 2
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: -
• Frequency: 500kHz ~ 650kHz, 900kHz ~ 1.1MHz
• Voltage - Supply: 4 V ~ 26.5 V
• Voltage - Output: 45V
• Mounting Type: Surface Mount
• Package / Case: 16-WFQFN Exposed Pad
• Operating Temperature: -40°C ~ 85°C
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Maximum DC Current Setting
The initial brightness should be set by choosing an appropriate
value for R
possible LED current as shown in Equation 2 for ISL97682 and
Equation 3 for ISL97683 and ISL97684:
DC Current Adjustment
Once R
For example, in the 4-channel ISL97684, if the maximum required
LED current (I
Equation 4:
PWM Control
The ISL97682, ISL97683, ISL97684 have high speed 8-bit
digitizers that decode the incoming PWM signal and convert it into
2- 3- or 4- channels of 8-bit PWM current with a phase shift
function that will be described later. During the PWM On period,
the LED peak current is defined by the R
average LED current of each channel is controlled by I
the PWM duty cycle in percent shown by Equation 5:
When the PWM input = 0, all channels are disconnected and the
I
The PWM dimming frequency is adjusted by a resistor at the
RFPWM pin, described in “PWM Dimming Frequency
Adjustment” on page 12.
I
I
R
I
LED
LEDmax
LEDmax
LED ave
SET
FIGURE 20. CONVENTIONAL 4-Ch LED DRIVER WITH 10% PWM
(
is guaranteed to be <5µA in this state.
=
SET
ILED_Total_80mA
(
)
402
=
=
=
SET
is fixed, the LED DC current can be adjusted.
(
-------------- -
(
-------------- -
R
R
ILED1-20mA
ILED2-20mA
ILED3-20mA
ILED4-20mA
804
402
I
) 0.02
LEDmax
SET
SET
LED(max)
. This should be chosen to fix the maximum
⁄
DIMMING CHANNEL CURRENT (UPPER) AND TOTAL
CURRENT (LOWER)
)
)
=
×
) is 20mA, rearranging Equation 3 yields
PWM
20.1kΩ
11
5
TIME (ms)
ISL97682, ISL97683, ISL97684
SET
10
resistor value. The
LEDmax
15
(EQ. 2)
(EQ. 3)
(EQ. 4)
(EQ. 5)
and
FIGURE 21. PHASE SHIFT 4-Ch LED DRIVER WITH 10% PWM
FIGURE 23. EQUAL PHASE SHIFT LED DRIVER PWM DIMMING
FIGURE 22. CONVENTIONAL LED DRIVER PWM DIMMING CHANNEL
ILED_Total_40mA
ILED_Total_80mA
ILED_Total_20mA
ILED4-20mA
ILED3-20mA
ILED2-20mA
ILED1-20mA
ILED4-20mA
ILED3-20mA
ILED2-20mA
ILED1-20mA
ILED1-20mA
ILED2-20mA
ILED3-20mA
ILED4-20mA
DIMMING CHANNEL CURRENT (UPPER) AND TOTAL
CURRENT (LOWER)
AND TOTAL CURRENT AT 50% DUTY CYCLE
CHANNEL AT 50% DUTY CYCLE
5
5
5
TIME (ms)
TIME (ms)
TIME (ms)
10
10
10
March 11, 2011
FN7689.0