CS51022A datasheet(9/11 Pages) ONSEMI

9 / 11 page

CS51021A, CS51022A, CS51023A, CS51024A

http://onsemi.com

Synchronization

A bi−directional synchronization is provided to synchronize

several controllers. When SYNC pins are connected together,

the converters will lock to the highest switching frequency. The

fastest controller becomes the master, producing a 4.3 V, 200

ns pulse train. Only one, the highest frequency SYNC signal,

will appear on the SYNC line.

Sleep

The sleep input is an active high input. The CS51022A/4A

is placed in sleep mode when SLEEP is driven high. In sleep

mode, the controller and MOSFET are turned off. Connect

to GND for normal operation. The sleep mode operates at

VCC

≤ 15 V.

Oscillator and Duty Cycle Limit

The switching frequency is set by RT and CT connected to

the RTCT pin. CT charges and discharges between 3.0 V and

1.5 V.

The maximum duty cycle is set by the ratio of the on time,

tON, and the whole period, T = tON + tOFF. Because the timing

capacitor’s discharge current is trimmed, the maximum duty

cycle is well defined. It is determined by the ratio between the

timing resistor RT and the timing capacitor CT. Refer to figures

6 and 7 to select appropriate values for RT and CT.

fSW +

TSW

;TSW + tCH ) tDIS

2500

RT (kW)

2000

1500

1000

500

100

RT (kW)

1. CT = 47 pF

2. CT = 100 pF

3. CT = 150 pF

4. CT = 220 pF

5. CT = 390 pF

6. CT = 470 pF

7. CT = 560 pF

8. CT = 680 pF

1. CT = 47 pF

2. CT = 100 pF

3. CT = 150 pF

4. CT = 220 pF

5. CT = 390 pF

6. CT = 470 pF

7. CT = 560 pF

8. CT = 680 pF

Figure 6. Frequency vs. RT for Discrete

Capacitor Values

Figure 7. Duty Cycle vs. RT for Discrete

Capacitor Values

ORDERING INFORMATION

Device

Package

Shipping†

CS51021AED16

SOIC−16

48 Units / Rail

CS51021AEDR16

2500 Tape & Reel

CS51021AEDR16G

SOIC−16

(Pb−Free)

CS51022ADBG

TSSOP−16*

48 Units / Rail

CS51022ADBR2G

TSSOP−16*

2500 Tape & Reel

CS51022AED16

SOIC−16

48 Units / Rail

CS51022AEDR16

2500 Tape & Reel

CS51022AEDR16G

SOIC−16

(Pb−Free)

CS51023AED16

SOIC−16

48 Units / Rail

CS51023AEDR16

2500 Tape & Reel

CS51023AEDR16G

SOIC−16

(Pb−Free)

†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging

Specifications Brochure, BRD8011/D.

*This package is inherently Pb−Free.

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