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MOSFET Selection/Considerations

The HIP6007 requires an N-Channel power MOSFET. It

requirements, and thermal management requirements.

In high-current applications, the MOSFET power

dissipation, package selection and heatsink are the

dominant design factors. The power dissipation includes

two loss components; conduction loss and switching loss.

The conduction losses are the largest component of power

dissipation for the MOSFET. Switching losses also

contribute to the overall MOSFET power loss (see the

equations below). These equations assume linear voltage-

current transitions and are approximations. The gate-

charge losses are dissipated by the HIP6007 and don't

heat the MOSFET. However, large gate-charge increases

MOSFET switching losses. Ensure that the MOSFET is

within its maximum junction temperature at high ambient

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 HIP6007. However, logic-level gate MOSFETs

can be used under special circumstances. The input voltage,

upper gate drive level, and the MOSFET’s absolute gate-to-

source voltage rating determine whether logic-level

MOSFETs are appropriate.

Figure 9 shows the upper gate drive (BOOT pin) supplied by

develops a floating supply voltage referenced to the PHASE

turns on. A logic-level MOSFET can only be used for Q1 if

the MOSFET’s absolute gate-to-source voltage rating

Figure 10 shows the upper gate drive supplied by a direct

connection to VCC. This option should only be used in

converter systems where the main input voltage is +5VDC

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

and 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 tradeoffs 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.

1

2

Fs is the switching frequency.

FIGURE 9. UPPER GATE DRIVE - BOOTSTRAP OPTION

+12V

HIP6007

GND

UGATE

PHASE

BOOT

VCC

+5V OR +12V

Q1

D2

NOTE:

+

-

+

-

+

-

+12V

HIP6007

GND

UGATE

PHASE

BOOT

VCC

+5V OR LESS

NOTE:

Q1

D2

HIP6007