Datasheet

 2006-2016 Microchip Technology Inc. DS20002019C-page 13
MCP1406/07
4.4 PCB Layout Considerations
Proper PCB layout is important in a high current,
fast switching circuit to provide proper device operation
and robustness of design. PCB trace loop area and
inductance should be minimized by the use of a ground
plane or ground trace located under the MOSFET gate
drive signals, separate analog and power grounds, and
local driver decoupling.
The MCP1406/07 devices have two pins each for V
DD
,
OUTPUT and GND. Both pins must be used for proper
operation. This also lowers path inductance which will,
along with proper decoupling, help minimize ringing in
the circuit.
Placing a ground plane beneath the MCP1406/07 will
help as a radiated noise shield as well as providing
some heat sinking for power dissipated within the
device.
4.5 Power Dissipation
The total internal power dissipation in a MOSFET driver
is the summation of three separate power dissipation
elements, which can be calculated by using the
following equation:
EQUATION 4-1:
4.5.1 CAPACITIVE LOAD DISSIPATION
The power dissipation caused by a capacitive load is a
direct function of frequency, total capacitive load and
supply voltage. The power lost in the MOSFET driver
for a complete charging and discharging cycle of a
MOSFET can be determined by means of this
equation:
EQUATION 4-2:
4.5.2 QUIESCENT POWER DISSIPATION
The power dissipation associated with the quiescent
current draw depends on the state of the input pin. The
MCP1406/07 devices have a quiescent current draw
when the input is high of 0.13 mA (typ) and 0.035 mA
(typ) when the input is low. The quiescent power dissi-
pation can be determined by using this equation:
EQUATION 4-3:
4.5.3 OPERATING POWER DISSIPATION
The operating power dissipation occurs each time the
MOSFET driver output transitions; this is because, for
a very short period of time, both MOSFETs in the output
stage are ON simultaneously. This cross-conduction
current leads to a power dissipation, as described by
the following equation:
EQUATION 4-4:
P
T
P
L
P
Q
P
CC
++=
Where:
P
T
= Total power dissipation
P
L
= Load power dissipation
P
Q
= Quiescent power dissipation
P
CC
= Operating power dissipation
P
L
fC
T
V
DD

2
=
Where:
f = Switching frequency
C
T
= Total load capacitance
V
DD
= MOSFET driver supply voltage
P
Q
I
QH
DI
QL
1 D–+V
DD
=
Where:
I
QH
= Quiescent current in the high state
D = Duty cycle
I
QL
= Quiescent current in the low state
V
DD
= MOSFET driver supply voltage
P
CC
CC f V
DD
=
Where:
CC = Cross-conduction constant (A sec.)
f = Switching frequency
V
DD
= MOSFET driver supply voltage