Dual High-Speed 1.5A MOSFET Drivers
The MAX4426/4427/4428 have easy-to-drive inputs.
However, these inputs must never be allowed to stay
for more than 50ns. Unused inputs
should always be connected to ground to minimize sup-
ply current. Drivers can be paralleled on the MAX4426 or
MAX4427 by tying both Inputs together and both outputs
Supply bypassing and grounding are extremely impor-
tant with the MAX4426/4427/4428, as the peak supply
current can be as high as 3A, which is twice the peak
output current. Ground drops are a form of negative
feedback with inverters, and hence will degrade the
delay and transition time of the MAX4426/MAX4428.
Suggested bypass capacitors are a 4.7µF (low ESR)
capacitor in parallel with a 0.1µF ceramic capacitor,
mounted as close as possible to the MAX4426/4427/4428.
Use a ground plane if possible or separate ground
returns for inputs and outputs. Output voltage ringing
can be minimized with a 5Ω to 20Ω resistor in series with
the output, but this will degrade output transition time.
Ringing may be undesirable due to the large current that
flows through capacitive loads when the voltage across
these loads transitions quickly.
Operation at the upper end of the supply voltage range
(> 15V) requires that a capacitance of at least 50pF be
present at the outputs. This prevents the supply voltage
provided to the die (which can be different from that
seen at the Ie supply pin) from exceeding the 20V abso-
lute maximum rating, due to overshoot. Since at least
50pF of gate capacitance is present in all higher power
FETs, this requirement is easily met.
The MAX4426/4427/4428 power dissipation consists of
input inverter losses, crowbar current through the output
devices, and output current (either capacitive or resis-
tive). The sum of these must be kept below the maximum
power dissipation limit.
The DC input inverter supply current is 0.2mA when both
inputs are low and 2mA when both inputs are high. The
crowbar current through an output device making a tran-
sition is approximately 100mA for a few nanoseconds.
This is a small portion of the total supply current, except
for high switching frequencies or a small load capaci-
The MAX4426/4427/4428 power dissipation when driv-
ing a ground-referenced resistive load is:
P = (D) (r
where D is the percentage of time the MAX4426/4427/4428
output pulls high, r
is the MAX4426/4427/4428
maximum on resistance, and I
is the MAX4426/4427/
4428 load current.
For capacitive loads. the power dissipation is:
P = (C
is the capacItive load. V
MAX4426/4427/4428 supply voltage, and FREO is the