ISL6446 Datasheet, PDF (3/20 Pages) Intersil Corporation – Dual (180° Out-of-Phase) PWM and Linear Controller

ISL6446
Pin Descriptions (Continued)
SYMBOL
RT
SS1/EN1
SS2/EN2
LCFB
LCDR
OCSET1, 2
PIN #
DESCRIPTION
5 This is the operating frequency adjustment pin. By placing a resistor from this pin to SGND, the oscillator frequency can be
programmed from 100kHz to 2.5MHz.
2, 11
These pins provide enable/disable and soft-start function for their respective controllers. The output is held off when the pin is
pulled to ground. When the chip is enabled, the regulated 30µA pull-up current source charges the capacitor connected from the
pin to ground. The output voltage of the converter follows the ramping voltage on the SS/EN pin. See “Soft-Start and Voltage
Tracking” on page 12 for more details.
8 This pin is the feedback pin for the linear controller. An external voltage divider network connected to this pin sets the output
voltage of the linear controller. If the linear controller is not used, tie this pin to VCC.
7 Open drain output PNP Transistor or P channel MOSFET Driver. LCDR connects to the base of an external PNP pass transistor or
the gate of the MOSFET to form a positive linear regulator. A small resistor can be inserted between the LCDR and the base of
the PNP pass transistor or the gate of the MOSFET to alleviate thermal stress at output short condition.
1, 12
These pins are the overcurrent set points for the respective PWM controllers. Connect a resistor (R_OCSET) from this pin to the
drain of the upper MOSFET. R_OCSET, an internal 110µA current source, and the upper MOSFET ON-resistance r_DS(ON) set the
converter overcurrent (OC) trip point according to Equation 1:
I_OC
=
I_{--O-----C----S----E----T-----}•_----R_{----O-----C----S----E----T--}
r_DS(ON)
(EQ. 1)
I_OC includes the DC load current, as well as the ripple current. An overcurrent trip initiates hiccup mode.
The voltage on the OCSET pin should not exceed 0.7V above the VIN pin voltage for proper current sensing when the UGATE is
turned on.
Ordering Information
PART NUMBER
(Notes 1, 2, 3)
PART
MARKING
TEMP.
RANGE (°C)
PACKAGE
(Pb-free)
PKG.
DWG. #
ISL6446IAZ
ISL 6446IAZ
-40 to +85
24 Ld QSOP
M24.15
NOTES:
1. Add “-T*” suffix for tape and reel. Please refer to TB347 for details on reel specifications.
2. These Intersil Pb-free plastic packaged products employ special Pb-free material sets, molding compounds/die attach materials, and 100% matte
tin plate plus anneal (e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations). Intersil
Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
3. For Moisture Sensitivity Level (MSL), please see device information page for ISL6446. For more information on MSL please see tech brief TB363.
3
FN7944.0
July 10, 2012