NCP5331 datasheet(35/38 Pages) ONSEMI

35 / 38 page

NCP5331

http://onsemi.com

VILIM + (IOUT,LIM ) DILo 2) @ (RLMAX ) RPCB,MAX)

@ GILIM

+ (72 A ) 7.20 A 2) @ (1.28 mW ) 0.26 mW)

@ 12 V V

+ 1.4 Vdc

Set the voltage at the ILIM pin using a resistor divider from

the 5.0 V reference output as shown in Figure 42. If the

resistor from ILIM to GND is chosen to be 910 Ω (RLIM2),

then the resistor from ILIM to 5.0 VREF can be calculated

from

RLIM1 + (VREF * VILIM) (VILIM RLIM2)

+ (5.0 V * 1.4 V) (1.4 V 910 W)

+ 2340 W or 2.37 kW

10. Overcurrent Timer

To set the overcurrent timer, solve Equation 35 for COVC

and substitute tOVC = 120 ms.

COVC + tOVC (5.5

105)

(35)

+ 120 ms (5.5

105)

+ 0.218 mFor 0.22 mF

11. Soft Start Time

To set the Soft Start time, first calculate the external ramp

size at a duty-cycle of D = 1.225 V/12 V = 0.102.

Ext_Ramp

+ D @

(VIN * VOUT)

(RSx @ CSx @ fSW)

+ 0.102 @

(12 V

* 1.225 V)

(10.0 k

W @ 0.1 mF @ 200 kHz)

+ 5.5 mV

RLIM2

910

RLIM1

5 VREF

To ILIM Pin

VLIM

Figure 42. Setting the Current Limit

Then calculate the steady-state COMP voltage.

VCOMP + VOUT @0A ) Channel_Startup_Offset

) Int_Ramp ) GCSA @ Ext_Ramp 2

+ 1.225 V ) 0.60 V ) 0.102 @ 250 mV

) 4.0 V V @ 5.3 mV 2

+ 1.86 V

Finally, solve Equation 35 for the soft-start capacitor,

CC2, and substitute as required.

CC2 + (tSS @ ICOMP) (VCOMP * RC1 @ ICOMP) (36)

+ (6 ms @ 30 mA) (1.86 V * 7.5 kW @ 30 mA)

+ 0.11 mFor 0.1 mF

12. Power Good Delay Time

First, use the previously derived value for ROSC to

calculate the current that will be supplied to the CPGD

capacitor.

IPGD + 0.52 V ROSC

+ 0.52 V 51 kW

+ 10.2 mA

Next, solve equation 37 for CPGD and substitute as

required.

CPGD + tPGD @ IPGD (PGDTHRESH * PGDMIN) (37)

+ 6ms @ 10.2 mA (3.0 V * 0.25 V)

+ 0.022 mF

NCP5331 Datasheet(PDF) 35 Page - ON Semiconductor

NCP5331 Datasheet(HTML) 35 Page - ON Semiconductor

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

Datasheet Download

Link URL