ISL6269AEVAL2Z Intersil, ISL6269AEVAL2Z Datasheet - Page 7

• Manufacturer Part Number: ISL6269AEVAL2Z
• Description: EVALUATION BOARD FOR ISL6269A
• Manufacturer: Intersil
• Series: Robust Ripple Regulator™ (R³)r

Specifications of ISL6269AEVAL2Z

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.1V or 1.2V
• Current - Output: 5A
• Voltage - Input: 5 ~ 25V
• Regulator Topology: Buck
• Frequency - Switching: 300kHz or 600kHz
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6269A, ISL6269B
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

LG (Pin 11)
The LG pin is the output of the low-side MOSFET gate
driver. Connect to the gate of the low-side MOSFET.
PVCC (Pin 12)
The PVCC pin is the input voltage bias for the LG low-side
MOSFET gate driver. Connect +5V from the PVCC pin to the
PGND pin. Decouple with at least 1µF of an MLCC capacitor
across the PVCC and PGND pins.
BOOT (Pin 13)
The BOOT pin stores the input voltage for the UG high-side
MOSFET gate driver. Connect an MLCC capacitor across
the BOOT and PHASE pins. The boot capacitor is charged
through an internal boot diode connected from the PVCC pin
to the BOOT pin, each time the PHASE pin drops below
PVCC minus the voltage dropped across the internal boot
diode.
UG (Pin 14)
The UG pin is the output of the high-side MOSFET gate
driver. Connect to the gate of the high-side MOSFET.
PHASE (Pin 15)
The PHASE pin detects the voltage polarity of the PHASE
node and is also the current return path for the UG high-side
MOSFET gate driver. Connect the PHASE pin to the node
consisting of the high-side MOSFET source, the low-side
MOSFET drain, and the output inductor.
PGOOD (Pin 16)
The PGOOD pin is an open-drain output that indicates when
the converter is able to supply regulated voltage. Connect
the PGOOD pin to +5V through a pull-up resistor.
Theory of Operation
Modulator
The ISL6269A is a hybrid of fixed frequency PWM control,
and variable frequency hysteretic control. Intersil’s R
technology can simultaneously affect the PWM switching
frequency and PWM duty cycle in response to input voltage
and output load transients. The term “Ripple” in the name
“Robust-Ripple-Regulator” refers to the converter output
inductor ripple current, not the converter output ripple
voltage. The R
which is an ideal representation of the output inductor ripple
current. The duty-cycle of V
discharge current through a ripple capacitor C
through C
that measures the VIN and VO pin voltages. The positive
slope of V
V
RPOS
=
R
R
(
g
is provided by a transconductance amplifier g
can be written as:
m
) V
3
•
(
modulator synthesizes an AC signal V
IN
–
V
OUT
)
R
is the result of charge and
7
R
. The current
3
(EQ. 1)
R
,
m
ISL6269A
The negative slope of V
Where g
A window voltage V
amplifier output voltage V
which the ripple voltage V
V
pins. The V
comparator in which V
and V
PWM pulses being generated as V
V
proportional to the slew rates of the positive and negative
slopes of V
proportional to the voltage between V
Power-On Reset
The ISL6269A is disabled until the voltage
increased above the rising power-on reset (POR)
threshold voltage. The controller will become once again
disabled when the voltage
POR
EN, Soft-Start, and PGOOD
The ISL6269A uses a digital soft-start circuit to ramp the
output voltage of the converter to the programmed regulation
setpoint at a predictable slew rate. The slew rate of the
soft-start sequence has been selected to limit the inrush
current through the output capacitors as they charge to the
desired regulation voltage. When the EN pin is pulled above
the rising EN threshold voltage V
Soft-Start Delay t
rise. The output voltage enters regulation in approximately
1.5ms and the PGOOD pin goes to high impedance once t
has elapsed.
V
W
COMP
RNEG
Ripple Capacitor Voltage C R
FIGURE 3. MODULATOR WAVEFORMS DURING LOAD
is set by a resistor connected across the FSET and GND
V
W
VCC_THF
=
thresholds . The PWM switching frequency is
m
is the higher threshold voltage. Figure 3 shows
g
is the gain of the transconductance amplifier.
R;
m
R,
⋅
TRANSIENT
the PWM switching frequency is inversely
V
V
COMP,
threshold voltage.
OUT
SS
W
starts and the output voltage begins to
is referenced with respect to the error
COMP
and V
R
COMP
R
can be written as:
V
is compared. The amplitude of
VCC
W
is the lower threshold voltage
signals feed into a window
Error Amplifier Voltage V COMP
, creating an envelope into
ENTHR
decreases below the falling
R
Window Voltage V W
traverses the V
W
the PGOOD
and V
PWM
V
VCC
COMP.
has
V
May 30, 2007
VCC_THR
W
FN9253.2
(EQ. 2)
and
SS