ISL6402EVAL4 Intersil, ISL6402EVAL4 Datasheet - Page 10
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ISL6402EVAL4
Manufacturer Part Number
ISL6402EVAL4
Description
EVALUATION BOARD ISL6402
Manufacturer
Intersil
Datasheet
1.ISL6402IR.pdf
(19 pages)
Specifications of ISL6402EVAL4
Main Purpose
DC/DC, Step Down with LDO
Outputs And Type
3, Non-Isolated
Voltage - Output
1.2V, 2.5V, 3.3V
Voltage - Input
4.5 ~ 24V
Regulator Topology
Buck
Frequency - Switching
300kHz
Board Type
Fully Populated
Utilized Ic / Part
ISL6402
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Pin Descriptions
BOOT2, BOOT1 - These pins power the upper MOSFET
drivers of each PWM converter. Connect this pin to the
junction of the bootstrap capacitor and the cathode of the
bootstrap diode. The anode of the bootstrap diode is
connected to the VCC_5V pin.
UGATE2, UGATE1 - These pins provide the gate drive for
the upper MOSFETs.
PHASE2, PHASE1 - These pins are connected to the junction
of the upper MOSFETs source, output filter inductor and lower
MOSFETs drain.
LGATE2, LGATE1 - These pins provide the gate drive for
the lower MOSFETs.
PGND - This pin provides the power ground connection for
the lower gate drivers for both PWM1 and PWM2. This pin
should be connected to the sources of the lower MOSFETs
and the (-) terminals of the external input capacitors.
FB3, FB2, FB1 - These pins are connected to the feedback
resistor divider and provide the voltage feedback signals for
the respective controller. They set the output voltage of the
converter. In addition, the PGOOD circuit uses these inputs
to monitor the output voltage status.
ISEN2, ISEN1 - These pins are used to monitor the voltage
drop across the lower MOSFET for current loop feedback
and overcurrent protection.
PGOOD - This is an open drain logic output used to indicate
the status of the output voltages. This pin is pulled low when
either of the two PWM outputs is not within 10% of the
respective nominal voltage, or if the linear controller output is
less than 75% of it’s nominal value.
SGND - (Pin 20 on the TSSOP; Pin 17 on the QFN)
This is the small-signal ground, common to all 3 controllers,
and must be routed separately from the high current ground
(PGND). All voltage levels are measured with respect to this
pin. Connect the additional SGND pins to this pin. If using a
5V supply, connect this pin to VCC_5V. A small ceramic
capacitor should be connected right next to this pin for noise
decoupling.
VIN - Use this pin to power the device with an external
supply voltage with a range of 5.6V to 24V. For 5V ±10%
operation, connect this pin to VCC_5V.
VCC_5V - This pin is the output of the internal 5V linear
regulator. This output supplies the bias for the IC, the low
side gate drivers, and the external boot circuitry for the high
side gate drivers. The IC may be powered directly from a
single 5V (±10%) supply at this pin. When used as a 5V
supply input, this pin must be externally connected to V
The VCC_5V pin must be always decoupled to power
ground with a minimum of 4.7µF ceramic capacitor, placed
very close to the pin.
10
IN
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ISL6402
SYNC - This pin may be used to synchronize two or more
ISL6402 controllers. This pin requires a 1K resistor to
ground if used; connect directly to VCC_5V if not used.
SS1, SS2 - These pins provide a soft-start function for their
respective PWM controllers. When the chip is enabled, the
regulated 5µA pull-up current source charges the capacitor
connected from this pin to ground. The error amplifier
reference voltage ramps from 0 to 0.8V while the voltage on
the soft-start pin ramps from 0 to 0.8V.
SD1, SD2 - These pins provide an enable/disable function
for their respective PWM output. The output is enabled when
this pin is floating or pulled HIGH, and disabled when the pin
is pulled LOW.
GATE3 - This pin is the open drain output of the linear
regulator controller.
OCSET2, OCSET1 - A resistor from this pin to ground sets
the overcurrent threshold for the respective PWM.
Functional Description
General Description
The ISL6402 integrates control circuits for two synchronous
buck converters and one linear controller. The two
synchronous bucks operate out of phase to substantially
reduce the input ripple and thus reduce the input filter
requirements. The chip has four control lines (SS1, SD1,
SS2, and SD2), which provide independent control for each
of the synchronous buck outputs.
The buck PWM controllers employ a free-running frequency
of 300kHz. The current mode control scheme with an input
voltage feed-forward ramp input to the modulator provides
excellent rejection of input voltage variations and provides
simplified loop compensations.
The linear controller can drive either a PNP or PFET to
provide ultra low-dropout regulation with programmable
voltages.
Internal 5V Linear Regulator (Vcc_5V)
All ISL6402 functions are internally powered from an on-
chip, low dropout 5V regulator. The maximum regulator input
voltage is 24V. Bypass the regulator’s output (Vcc_5V) with
a 4.7µF capacitor to ground. The dropout voltage for this
LDO is typically 600mV, so when Vcc_5V is greater then
5.6V, Vcc_5V is typically 5V. The ISL6402 also employs an
undervoltage lockout circuit that disables both regulators
when Vcc_5V falls below 4.4V.
The internal LDO can source over 60mA to supply the IC,
power the low side gate drivers, charge the external boot
capacitor and supply small external loads. When driving
large FETs especially at 300kHz frequency, little or no
regulator current may be available for external loads.
November 8, 2004
FN9123.3