DATASHEET
ISL6534
Dual PWM with Linear
The ISL6534 is a versatile triple regulator that has two
independent synchronous-rectified buck controllers with
integrated 12V gate drivers (OUT1 and OUT2) and a linear
controller (OUT3) to offer precision regulation of up to three
voltage rails. An optional shunt regulator allows 12V only
operation, when a 5V supply is not available.
Each controller has independent soft-start and enable
functions combined on a single pin. A capacitor from each
SS/EN pin to ground sets the soft-start time, and pulling
SS/EN below 1.0V disables the controller. The SS/EN pins
can be controlled independently or they can be ganged
together to provide complete control of start-up coordination.
The PGOOD function indicates when all regulators have
completed their soft-start and provides an indication of short-
circuit conditions on either switching regulator.
There are two ways to control the switching frequency of the
PWM regulators. The default switching frequency is 300kHz
(FS_SYNC to ground). A resistor from FS_SYNC to ground
increases the switching frequency (up to 1MHz). Connecting
the gate signal from another PWM IC synchronizes the
ISL6534 switchers to the frequency of the other controller.
This allows independent regulators operating at a common
frequency to avoid low-frequency beats. The gate drivers for
DDR mode can be staggered by 90° in order to minimize
cross-conduction.
Switcher OUT1 has an internal reference for regulating any
voltage down to 0.6V. OUT2 has current sinking capability
and an external reference input allowing convenient
connection to OUT1 through a resistor divider for DDRAM
applications. The 3.3V reference pin provides the option for
independent regulation of OUT2. The linear controller drives
an external N-Channel MOSFET, making the ISL6534 one of
the most versatile regulators available.
FN9134
Rev 2.00
Nov 18, 2005
Features
• Two Synchronous-Rectified Buck Controllers
- Voltage Mode Control
- VIN Range up to 12V
- VOUT Range from 0.6V to 6V
- 12V LGATE Drivers; up to 12V Boot Strap for UGATE
• Switcher References
- 0.6V Reference for OUT1
- 3.3V Reference Output for OUT2
- External Reference Input for OUT2
- Buffered VTT Reference Output
• Switcher Clocking
- Phase Options for Optimal Clock Relationship
- Resistor-Selectable Switching Frequency (300kHz
default; Resistor to Ground for 300kHz to 1MHz range)
- Synchronization-Capable Switching Frequency
(Connect FS_SYNC to Separate Regulator)
• Single Linear Controller
- Drives N-Channel MOSFET
- 0.6V Reference
- VIN Range up to 12V
- VOUT Range from 0.6V to 3.3V
• 12V and 5V Supplies Required (but optional shunt
regulator can generate VCC = 5.8V from 12V)
• Three Independent Soft-Start/Enable Pins
- Gang Together or Control Independently
• PGOOD Output Indicates All Outputs Available
• Thermally Enhanced QFN or TSSOP Package
• QFN Package:
- Compliant to JEDEC PUB95 MO-220
QFN - Quad Flat No Leads - Package Outline
- Near Chip Scale Package footprint, which improves
PCB efficiency and has a thinner profile
• Pb-Free Plus Anneal Available (RoHS Compliant)
Simplified Block Diagram
SS1/EN1
COMP1
FB1
SS2/EN2
REFIN
FB2
COMP2
OUT1
PWM CONTROLLER
BOOT1
UGATE1
LGATE1
BOOT2
UGATE2
LGATE2
REFOUT
VREF
SS3/EN3
FB3
3.3V
OUT3
LINEAR CONTROLLER
PGOOD
FS/SYNC
DRIVE3
OUT2
PWM CONTROLLER
FN9134 Rev 2.00
Nov 18, 2005
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