ISL97674IRZ Intersil, ISL97674IRZ Datasheet - Page 10

• Manufacturer Part Number: ISL97674IRZ
• Description: IC LED DVR PWM CTRL 6CH 20QFN
• Manufacturer: Intersil

Specifications of ISL97674IRZ

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Automotive, Backlight
• Type - Secondary: RGB, White LED
• Frequency: 600kHz, 1.2MHz
• Voltage - Supply: 4.5 V ~ 26.5 V
• Voltage - Output: *
• Mounting Type: Surface Mount
• Package / Case: 20-VFQFN Exposed Pad
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 40mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Typical Performance Curves
FIGURE 15. LINE REGULATION WITH V
FIGURE 17. LOAD REGULATION WITH I
Theory of Operation
PWM Boost Converter
The current mode PWM boost converter produces the
minimal voltage needed to enable the LED stack with the
highest forward voltage drop to run at the programmed
current. The ISL97674 employ current mode control
boost architecture that has a fast current sense loop and
a slow voltage feedback loop. Such architecture achieves
a fast transient response that is essential for the
notebook backlight application where the power can be a
series of drained batteries or instantly change to an
AC/DC adapter without rendering a noticeable visual
nuisance. The number of LEDs that can be driven by
ISL97674 depend on the type of LED chosen in the
application. The ISL97674 are capable of boosting up to
45V and typically driving 13 LEDs in series for each of the
6 channels, enabling a total of 78 pieces of the
3.2V/20mA type of LEDs.
FROM 26V TO 6V FOR 6P12S AT
20mA/CHANNEL
FROM 100% TO 0% PWM DIMMING,
V
IN
= 12V, 6P12S AT 20mA/CHANNEL
10
IN
LED
CHANGE
CHANGE
ISL97674
(Continued)
FIGURE 16. LOAD REGULATION WITH I
Enable and PWM
The ISL97674 has EN/PWM pin that serves dual
purposes; it is used as an Enable signal and can be used
as a PWM input signal for dimming. If a PWM signal is
applied to this pin, the first pulse of minimum 4ms will be
used as an Enable signal. If there is no signal for longer
than 28ms, the device will enter shutdown.
Current Matching and Current Accuracy
Each channel of the LED current is regulated by the
current source circuit, as shown in Figure 19.
FIGURE 18. ISL97671 SHUTS DOWN AND STOPS
SWITCHING ~ 30ms AFTER EN GOES LOW
FROM 0% TO 100% PWM DIMMING,
V
IN
= 12V, 6P12S AT 20mA/CHANNEL
LED
CHANGE
June 25, 2010
FN7634.0