ISL6540_06 Datasheet, PDF (9/20 Pages) Intersil Corporation – Single-Phase Buck PWM Controller with Integrated High Speed MOSFET Driver and Pre-Biased Load Capability

ISL6540
Functional Pin Description
VSEN+ (Pin 1)
This pin provides differential remote sense for the ISL6540.
It is the positive input of a standard instrumentation amplifier
topology with unity gain, and should connect to the positive
rail of the load/processor. The voltage at this pin should be
set equal to the internal system reference voltage (0.591V
typical.)
VSEN- (Pin 2)
This pin provides differential remote sense for the regulator.
It is the negative input of the instrumentation amplifier, and
should connect to the negative rail of the load/processor.
Typically 50µA is sourced from this pin. The output of the
remote sense buffer is disabled (High Impedance) by pulling
VSEN- to VCC.
REFOUT (Pin 3)
This pin connects to the unmargined system reference
through an internal buffer. It has a 19mA drive capability with
an output common mode range of GND to VCC. The
REFOUT buffer requires at least 1µF of capacitive loading to
be stable. This pin should not be left floating.
REFIN (Pin 4)
When the external reference pin (REFIN) is NOT within ~800
mV of VCC, the REFIN pin is used as the system reference
instead of the internal 0.591V reference. The recommended
REFIN input voltage range is ~60mV to VCC - 1.8V.
SS (Pin 5)
This pin provides softstart functionality for the ISL6540. A
capacitor connected to ground along with the internal 38mA
Operational Transconductance Amplifier (OTA), sets the
soft-start interval of the converter. This pin is directly
connected to the non-inverting input of the Error Amplifier.
To prevent noise injection into the error amplifier the SS
capacitor should be located within 150 mils of the SS and
GND pins.
OFS+ (Pin 6)
This pin sets the positive margining offset voltage. Resistors
should be connected to GND (R_OFS+ ) and OFS-( R_MARG)
from this pin. With MAR_CTRL logic low, the internal 0.591V
reference is developed at the OFS+ pin across resistor
R_OFS+. The voltage on OFS+ is driven from OFS- through
R_MARG. The resulting voltage differential between OFS+
and OFS- is divided by 5 and imposed on the system
reference. The maximum designed offset of 1V between
OFS+ and OFS- pins translates to a 200mV offset.
OFS- (Pin 7)
This pin sets the negative margining offset voltage.
Resistors should be connected to GND (R_OFS- ) and OFS+
(R_MARG) from this pin. With MAR_CTRL logic low, the
internal 0.591V reference is developed at the OFS- pin
across resistor R_OFS-. The voltage on OFS- is driven from
OFS+ through R_MARG. The resulting voltage differential
between OFS+ and OFS- is divided by 5 and imposed on the
system reference. The maximum designed offset of -1V
between OFS+ and OFS- pins translates to a -200mV offset
of the system reference.
VCC (Pin 8, Analog Circuit Bias)
This pin provides power for the ISL6540 analog circuitry.
The pin should be connected to a 2.9V to 5.6V bias through
an RC filter from PVCC to prevent noise injection into the
analog circuitry. This pin can be powered off the internal or
external linear regulator options.
MARCTRL (Pin 9)
The MARCTRL pin controls margining function, a logic high
enables positive margining, a logic low sets negative
margining, a high impedance disables margining.
PG_DLY (Pin 10)
Provides the ability to delay the output of the PGOOD
assertion by connecting a capacitor from this pin to GND. A
0.1µF capacitor produces approximately a 5ms delay.
PGOOD (Pin 11)
Provides an open drain Power Good signal when the output
is within 9% of nominal output regulation point with 6%
hysteresis (15%/9%), and after soft-start is complete.
PGOOD monitors the VMON pin.
EN (Pin 12)
This pin is compared with an internal 0.49V reference and
enables the soft-start cycle. This pin also can be used for
voltage monitoring. A 10µA current source to GND is active
while the part is disabled, and is inactive when the part is
enabled. This provides functionality for programmable
hysteresis when the EN pin is used for voltage monitoring.
VFF (Pin 13)
The voltage at this pin is used for input voltage feed forward
compensation and sets the internal oscillator ramp peak to
peak amplitude at 0.16 * VFF. An external RC filter may be
required at this pin in noisy input environments. The
minimum recommended VFF voltage is 2.97V.
VIN (Pin 14, Internal Linear Regulator Input)
This pin should be tied directly to the input rail when using
the internal or external linear regulator options. It provides
power to the External/Internal Linear drive circuitry. When
used with an external 3.3V to 5V supply, this pin should be
tied directly to PVCC.
9
FN9214.0
March 9, 2006