CAT661 Ver la hoja de datos (PDF) - ON Semiconductor

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Fabricante

CAT661

High Frequency 100 mA CMOS Charge Pump, Inverter/Doubler

ON Semiconductor 

CAT661

Capacitor Selection

Low ESR capacitors are necessary to minimize voltage

losses, especially at high load currents. The exact values of

C1 and C2 are not critical but low ESR capacitors are

necessary.

The ESR of capacitor C1, the pump capacitor, can have a

pronounced effect on the output. C1 currents are

approximately twice the output current and losses occur on

both the charge and discharge cycle. The ESR effects are

thus multiplied by four. A 0.5 Ω ESR for C1 will have the

same effect as a 2 Ω increase in CAT661 output impedance.

Output voltage ripple is determined by the value of C2 and

the load current. C2 is charged and discharged at a current

roughly equal to the load current. The internal switching

frequency is one−half the oscillator frequency.

VRIPPLE + IOUTń(FOSC C2) ) IOUT ESRC2

For example, with a 25 kHz oscillator frequency

(12.5 kHz switching frequency), a 150 mF C2 capacitor with

an ESR of 0.2 Ω and a 100 mA load peak−to−peak ripple

voltage is 45 mV.

Table 5. VRIPPLE vs. FOSC

VRIPPLE (mV)

IOUT (mA)

45

100

25

100

FOSC (kHz)

25

135

C2 (mF)

150

150

C2 ESR (W)

0.2

0.2

V+

BOOST/FC

(1)

7.0 I

I

OSC

(7)

~18 pF

7.0 I

I

LV

(6)

REQUIRED FOR TTL LOGIC

NC

+

C1

CAT661

1

BOOST/FC

V+ 8

2 CAP+

7

OSC

3 GND

6

LV

4

5

CAP−

OUT

100 k

−V+

C2

+

V+

OSC

INPUT

Figure 22. Oscillator

Figure 23. External Clocking

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