ISL97684IRTZ-T Intersil, ISL97684IRTZ-T Datasheet - Page 11
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ISL97684IRTZ-T
Manufacturer Part Number
ISL97684IRTZ-T
Description
4 Channel LED Driver, 16LD TQFN 3X3, T&R
Manufacturer
Intersil
Series
-r
Datasheet
1.ISL97682IRTZ.pdf
(17 pages)
Specifications of ISL97684IRTZ-T
Constant Current
-
Constant Voltage
-
Topology
PWM, Step-Up (Boost)
Number Of Outputs
4
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