Undervoltage Lockout

Both the high- and low-side drivers feature undervolt-

threshold is referenced to GND and pulls both driver

driver has its own undervoltage lockout threshold

BST falls below 6.4V with respect to HS.

old, DL starts switching and follows the IN_L logic input.

At this time, the bootstrap capacitor is not charged and

nous buck and half-bridge converter topologies, the

bootstrap capacitor can charge up in one cycle and

normal operation begins in a few microseconds after the

forward topology, the BST capacitor takes some time (a

few hundred microseconds) to charge and increase its

The typical hysteresis for both UVLO thresholds is 0.5V.

The bootstrap capacitor value should be selected care-

fully to avoid unintentional oscillations during turn-on

and turn-off at the DH output. Choose the capacitor

value about 20 times higher than the total gate capaci-

tance of the MOSFET. Use a low-ESR-type X7R dielec-

tric ceramic capacitor at BST (typically a 0.1µF ceramic

is adequate) and a parallel combination of 1µF and

(MAX5062_, MAX5063_) or to PGND (MAX5064_). The

high-side MOSFET’s continuous on-time is limited due

to the charge loss from the high-side driver’s quiescent

current. The maximum on-time is dependent on the size

Output Driver

The MAX5062/MAX5063/MAX5064 have low 2.5

Ω

in the output stage. This allows for a fast turn-on and

turn-off of the high gate-charge switching MOSFETs.

The peak source and sink current is typically 2A.

Propagation delays from the logic inputs to the driver

outputs are matched to within 8ns. The internal p- and

n-channel MOSFETs have a 1ns break-before-make

logic to avoid any cross conduction between them. This

internal break-before-make logic eliminates shoot-

through currents reducing the operating supply current

sink currents and faster switching speeds.

Internal Bootstrap Diode

used in conjunction with a bootstrap capacitor external-

ly connected between BST and HS. The diode charges

side driver turns on (see the Typical Operating Circuit).

The internal bootstrap diode has a typical forward volt-

age drop of 0.9V and has a 10ns typical turn-off/turn-on

Programmable Break-Before-Make

(MAX5064)

Half-bridge and synchronous buck topologies require

that the high- or low-side switch be turned off before

the other switch is turned on to avoid shoot-through

currents. Shoot-through occurs when both high- and

low-side switches are on at the same time. This condi-

tion is caused by the mismatch in the propagation

delay from IN_H/IN_L to DH/DL, driver output imped-

ance, and the MOSFET gate capacitance. Shoot-

through currents increase power dissipation, radiate

EMI, and can be catastrophic, especially with high

input voltages.

The MAX5064 offers a break-before-make (BBM) fea-

ture that allows the adjustment of the delay from the

input to the output of each driver. The propagation

delay from the rising edges of IN_H and IN_L to the ris-

ing edges of DH and DL, respectively, can be pro-

grammed from 16ns to 95ns. Note that the BBM time

because of the fixed comparator delay in the BBM

error. The low 8ns (maximum) delay mismatch reduces

The voltage at BBM is regulated to 1.3V. The BBM circuit

Bypass BBM to AGND with a 1nF or smaller ceramic

is stabilized before the UVLO clears the device turn-on.

Rk

t

ns

for R

k

tt

t

BBM

BBM

BBM

BBM ERROR

BBM

MATCH

.

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⎝⎜

⎞

⎠⎟

<

=×

+

−

10

8

1

200

015

ΩΩ

125V/2A, High-Speed,

Half-Bridge MOSFET Drivers

10

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