Pin Configuration
Applications Information
Power Dissipation
Power dissipation in the IC package comes mainly from
switching the MOSFETs. Therefore, it is a function of
both switching frequency and the total gate charge of
the selected MOSFETs. The total power dissipation
when both drivers are switching is given by:
where fSis the switching frequency, QG_TOTAL_HS is
the total gate charge of the selected high-side
MOSFET, QG_TOTAL_LS is the total gate charge of the
selected low-side MOSFET, N is the total number of the
high-side MOSFETs in parallel, M is the total number of
the low-side MOSFETs in parallel, VPV_ is the voltage at
the PV_ pin, RHS is the on-resistance of the high-side
driver, RLS is the on-resistance of the low-side driver,
RG_HS is the gate resistance of the selected high-side
MOSFET, RG_LS is the gate resistance of the selected
low-side MOSFETs, VVCC is the voltage at the VCC pin,
and IVCC is the supply current at the VCC pin.
PC Board Layout Considerations
The MAX8523 MOSFET driver sources and sinks large
currents to drive MOSFETs at high switching speeds.
The high di/dt can cause unacceptable ringing if the
trace lengths and impedances are not well controlled.
The following PC board layout guidelines are recom-
mended when designing with the MAX8523:
1) Place all decoupling capacitors (C2, C3, C4, C7) as
close to their respective pins as possible.
2) Minimize the high-current loops from the input capaci-
tor, upper-switching MOSFET, and low-side MOSFET
back to the input capacitor negative terminal.
3) Provide enough copper area at and around the
switching MOSFETs and inductors to aid in thermal
dissipation.
4) Connect the PGND1 and PGND2 pins of the
MAX8523 as close as possible to the source of the
low-side MOSFETs.
5) Keep LX1 and LX2 away from sensitive analog com-
ponents and nodes. Place the IC and analog com-
ponents on the opposite side of the board from the
power-switching node if possible.