ISL97672IRZ Intersil, ISL97672IRZ Datasheet - Page 15

• Manufacturer Part Number: ISL97672IRZ
• Description: IC LED DVR PWM CTRL 6CH 20QFN
• Manufacturer: Intersil

Specifications of ISL97672IRZ

• Constant Current: *
• Constant Voltage: *
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Automotive, Backlight
• Frequency: 200kHz ~ 1.5MHz
• 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

Schottky Diode
A high speed rectifier diode is necessary to prevent
excessive voltage overshoot, especially in the boost
configuration. Low forward voltage and reverse leakage
current will minimize losses, making Schottky diodes the
preferred choice. Although the Schottky diode turns on
only during the boost switch Off period, it carries the
same peak current as the inductor’s, and therefore, a
suitable current rated Schottky diode must be used.
Applications
High Current Applications
Each channel of the ISL97672 can support up to 30mA.
For applications that need higher current, multiple
channels can be grouped to achieve the desirable
current. For example, the cathode of the last LED can be
connected to CH0 to CH2; this configuration can be
treated as a single string with 90mA current driving
capability.
FIGURE 21. GROUPING MULTIPLE CHANNELS FOR
HIGH CURRENT APPLICATIONS
CH0
CH1
CH2
15
V
OUT
ISL97672
Compensation
The ISL97672 has two main elements in the system; the
Current Mode Boost Regulator and the op amp based
multi-channel current sources. The ISL97672
incorporates a transconductance amplifier in its feedback
path to allow the user some levels of adjustment on the
transient response and better regulation. The ISL97672
uses current mode control architecture, which has a fast
current sense loop and a slow voltage feedback loop. The
fast current feedback loop does not require any
compensation. The slow voltage loop must be
compensated for stable operation. The compensation
network is a series Rc, Cc1 network from COMP pin to
ground and an optional Cc2 capacitor connected to the
COMP pin. The Rc sets the high frequency integrator gain
for fast transient response and the Cc1 sets the
integrator zero to ensure loop stability. For most
applications, Rc is in the range of 15kΩ and Cc1 is in the
range of 2.2nF. Depends on the PCB layout, a Cc2, in
range of 47pF, may be needed to create a pole to cancel
the output capacitor ESR’s zero effect for stability.
November 1, 2010
FN7632.1