ISL6527EVAL2 Intersil, ISL6527EVAL2 Datasheet - Page 7

• Manufacturer Part Number: ISL6527EVAL2
• Description: EVALUATION BOARD QFN ISL6527
• Manufacturer: Intersil

Specifications of ISL6527EVAL2

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 0.75 ~ 3V
• Current - Output: 5A
• Voltage - Input: 3.3 ~ 5V
• Regulator Topology: Buck
• Frequency - Switching: 300kHz
• Board Type: Fully Populated
• Utilized Ic / Part: ISL6527
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

Electrical Specifications
NOTE:
Functional Description
Initialization
The ISL6527, ISL6527A automatically initialize upon receipt of
power. Special sequencing of the input supplies is not
necessary. The Power-On Reset (POR) function continually
monitors the the output voltage of the Charge Pump. During
POR, the Charge Pump operates on a free running oscillator.
Once the POR level is reached, the Charge Pump oscillator is
synched to the PWM oscillator. The POR function also initiates
the soft-start operation after the Charge Pump Output Voltage
exceeds its POR threshold.
Soft-Start
The POR function initiates the digital soft-start sequence. The
PWM error amplifier reference is clamped to a level
proportional to the soft-start voltage. As the soft-start voltage
slews up, the PWM comparator generates PHASE pulses of
increasing width that charge the output capacitor(s). This
method provides a rapid and controlled output voltage rise. The
soft-start sequence typically takes about 6.5ms when V
is 1.5V
If V
proportionally smaller as shown in Equation 2:
RiseTime
Figure 1 shows the soft-start sequence for a typical
application. At T0, the +3.3V VCC voltage starts to ramp. At
time t1, the Charge Pump begins operation and the +5V
CPVOUT IC bias voltage starts to ramp up. Once the voltage
on CPVOUT crosses the POR threshold at time t2, the output
begins the soft-start sequence. The triangle waveform from
the PWM oscillator is compared to the rising error amplifier
output voltage. As the error amplifier voltage increases, the
pulse-width on the UGATE pin increases to reach the
steady-state duty cycle at time t3.
PROTECTION/DISABLE
OCSET Current Source
Disable Threshold
4. Limits should be considered typical and are not production tested.
REF_IN
=
is less that 1.5V, the soft-start rise time will be
PARAMETER
t
SS
×
V
-------------------- -
REFIN
1.5V
7
Recommended Operating Conditions, unless otherwise noted V
V
SYMBOL
OCSET/SD
I
OCSET
Commercial
Industrial
ISL6527, ISL6527A
REF_IN
(EQ. 2)
TEST CONDITIONS
.
Shoot-Through Protection
A shoot-through condition occurs when both the upper
MOSFET and lower MOSFET are turned on simultaneously,
effectively shorting the input voltage to ground. To protect the
regulator from a shoot-through condition, the ISL6527,
ISL6527A incorporate specialized circuitry, which insures that
the complementary MOSFETs are not ON simultaneously.
The adaptive shoot-through protection utilized by the
ISL6527, ISL6527A looks at the lower gate drive pin, LGATE,
and the upper gate drive pin, UGATE, to determine whether a
MOSFET is ON or OFF. If the voltage from UGATE or from
LGATE to GND is less than 0.8V, then the respective
MOSFET is defined as being OFF and the complementary
MOSFET is turned ON. This method of shoot-through
protection allows the regulator to sink or source current.
Since the voltage of the lower MOSFET gate and the upper
MOSFET gate are being measured to determine the state of
the MOSFET, the designer is encouraged to consider the
repercussions of introducing external components between
the gate drivers and their respective MOSFET gates before
actually implementing such measures. Doing so may interfere
with the shoot-through protection.
0V
(1V/DIV)
FIGURE 1. SOFT-START INTERVAL
t0
t1
CC
t2
= 3.3V ±5% and T
MIN
18
16
-
TIME
t3
TYP
20
20
-
VOUT (2.50V)
A
VCC (3.3V)
= +25°C (Continued)
MAX
CPVOUT (5V)
0.8
22
22
November 18, 2008
UNITS
FN9056.10
µA
µA
V