NCP5183, NCV5183

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13

to 1% of nominal value, which is 150 mV. To

cover charge losses from eq. 2

C

Q

tot

V

ripple

+ 30.4n

0.15

+ 203 nF

(eq. 3)

It is recommended to increase the value as consumption

and gate charge are temperature and voltage dependent, so

let’s choose a capacitor 330 nF in this case.

To keep the application running properly, it is necessary

resistor value selection is critical for proper function of the

high side driver. If too small high current peaks are drown

to appropriate level and the high side driver can be disabled

by internal UVLO protection.

First of all keep in mind the capacitor is charged through

the external boot strap diode, so it can be charged to a

calculated using this equation:

R

t

charge

C

Vmax*VCmin

Vmax*VCmax

+

5

m

330n

14.4

*14.35

^

(eq. 4)

^ 11 W

Where:

period the low side MOSFET is turned on

forward voltage of used diode.

necessary to determine the target voltage for charging,

because in theory, when a capacitor is charged from a

voltage source through a resistor, the capacitor can never

reach the voltage of the source. In this particular case a

50 mV difference (between the voltage behind the diode and

The resistor value obtained from eq. 4 does not count with

will create another voltage drop of:

V

The current consumed by high side driver will be higher,

While switching, losses by charging and discharging

internal transistors as well as the level shifters will be added.

This current will increase with frequency.

The additional 0.9 mV drop can be either accepted or the

drop.

state conditions. During start and/or skip operation the

starting point voltage value is different (lower) and it takes

more time to charge the boot strap capacitor. More over it is

not counted with temperature and voltage variability during

normal operation or the dynamic resistance of the boot strap

diode (approximately 0.34

W for MURA160). From these

reasons the resistor value should be decreased especially

with respect to skip operation.

Boot strap resistor losses calculation.

P

(eq. 6)

Boot strap diode losses calculation.

P

(eq. 7)

Please keep in mind the value is temperature and voltage

calculated value. See “Layout recommendation” section for

more details.

Total Power Dissipation

The NCP5183 is suitable to drive high input capacitance

MOSFET, from this reason it is equipped with high current

capability drivers. Power dissipation on the die, especially

at high frequencies can be limiting factor for using this

driver. It is important to not exceed maximum junction

temperature (listed in absolute maximum ratings table) in

any cases. To calculate approximate power losses follow

these steps:

1. Power loss of device (except drivers) while

switching at appropriate frequency (see Figure 26)

is equal to

P

(eq. 8)

+ (14.4 @ 1.6m) ) (15 @ 0.6m) ^ 32.1 mW

2. Power loss of drivers

P

(eq. 9)

+ ((30n @ 14.4) ) (30n @ 15)) @ 100k ^ 88 mW

3. Total power losses

P

(eq. 10)

4. Junction temperature increase for calculated power

loss

t

(eq. 11)

The temperature calculated in eq. 11 is the value which has

to be added to ambient temperature. In case the ambient

temperature is 30

°C, the junction temperature will be 52°C.