10

temperature by calculating the temperature rise according

to package thermal-resistance specifications. A separate

heatsink may be necessary depending upon MOSFET

power, package type, ambient temperature and air flow.

Standard-gate MOSFETs are normally recommended for

use with the HIP6005. However, logic-level gate MOSFETs

can be used under special circumstances. The input voltage,

upper gate drive level, and the MOSFETs absolute

gate-to-source voltage rating determine whether logic-level

MOSFETs are appropriate.

Figure 10 shows the upper gate drive (BOOT pin) supplied

develops a floating supply voltage referenced to the PHASE

conducts. Logic-level MOSFETs can only be used if the

MOSFETs absolute gate-to-source voltage rating exceeds

Figure 11 shows the upper gate drive supplied by a direct

or less. The peak upper gate-to-source voltage is

power and +12VDC for the bias, the gate-to-source voltage

of Q1 is 7V. A logic-level MOSFET is a good choice for Q1

under these conditions.

Schottky Selection

Rectifier D2 conducts when the upper MOSFET Q1 is off. The

diode should be a Schottky type for low power losses. The

power dissipation in the schottky rectifier is approximated by:

In addition to power dissipation, package selection and

heatsink requirements are the main design trade-offs in

choosing the schottky rectifier. Since the three factors are

interrelated, the selection process is an iterative procedure.

The maximum junction temperature of the rectifier must

remain below the manufacturer’s specified value, typically

and the schottky power dissipation equation (shown above),

the junction temperature of the rectifier can be estimated. Be

sure to use the available airflow and ambient temperature to

determine the junction temperature rise.

+12V

HIP6005

GND

UGATE

PHASE

BOOT

VCC

+5V OR +12

FIGURE 10. UPPER GATE DRIVE - BOOTSTRAP OPTION

(NOTE)

Q1

D2

+

-

+12V

HIP6005

GND

UGATE

PHASE

BOOT

+5V OR LESS

Q1

+

-

D2

NOTE:

HIP6005