ISL6251HRZ View Datasheet(PDF) - Renesas Electronics
Part Name
Description
Manufacturer
ISL6251HRZ Datasheet PDF : 20 Pages
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ISL6251, ISL6251A
GND and VDD Pin
At least one high quality ceramic decoupling cap should be used
to cross these two pins. The decoupling cap can be put close to
the IC.
LGATE Pin
This is the gate drive signal for the bottom MOSFET of the buck
converter. The signal going through this trace has both high dv/dt
and high di/dt, and the peak charging and discharging current is
very high. These two traces should be short, wide, and away from
other traces. There should be no other traces in parallel with
these traces on any layer.
PGND Pin
PGND pin should be laid out to the negative side of the relevant
output cap with separate traces. The negative side of the output
capacitor must be close to the source node of the bottom
MOSFET. This trace is the return path of LGATE.
PHASE Pin
This trace should be short, and positioned away from other weak
signal traces. This node has a very high dv/dt with a voltage
swing from the input voltage to ground. No trace should be in
parallel with it. This trace is also the return path for UGATE.
Connect this pin to the high-side MOSFET source.
UGATE Pin
This pin has a square shape waveform with high dv/dt. It
provides the gate drive current to charge and discharge the top
MOSFET with high di/dt. This trace should be wide, short, and
away from other traces similar to the LGATE.
BOOT Pin
This pin’s di/dt is as high as the UGATE; therefore, this trace
should be as short as possible.
CSOP, CSON Pins
The current sense resistor connects to the CSON and the CSOP
pins through a low pass filter. The CSON pin is also used as the
battery voltage feedback. The traces should be away from the
high dv/dt and di/di pins like PHASE, BOOT pins. In general, the
current sense resistor should be close to the IC. Other layout
arrangements should be adjusted accordingly.
EN Pin
This pin stays high at enable mode and low at idle mode and is
relatively robust. Enable signals should refer to the signal ground.
DCIN Pin
This pin connects to AC adapter output voltage, and should be
less noise sensitive.
Copper Size for the Phase Node
The capacitance of PHASE should be kept very low to minimize
ringing. It would be best to limit the size of the PHASE node
copper in strict accordance with the current and thermal
management of the application.
Identify the Power and Signal Ground
The input and output capacitors of the converters, the source
terminal of the bottom switching MOSFET PGND should connect
to the power ground. The other components should connect to
signal ground. Signal and power ground are tied together at one
point.
Clamping Capacitor for Switching MOSFET
It is recommended that ceramic caps be used closely connected
to the drain of the high-side MOSFET, and the source of the low-
side MOSFET. This capacitor reduces the noise and the power
loss of the MOSFET.
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FN9202 Rev 3.00
March 13, 2014
Page 18 of 20
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