IP1844 查看數據表（PDF） - Semelab - > TT Electronics plc

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IP1844

CURRENT MODE REGULATING PULSE WIDTH MODULATORS

Semelab - > TT Electronics plc  

SEME

LAB

IP1844 SERIES

IP1845 SERIES

APPLICATIONS INFORMATION

Oscillator Waveforms and Maximum Duty Cycle

V REF 8

RT

RT CT 4

CT

GND 5

LARGE R T

SMALL C T

SMALL R T

LARGE C T

V - Pin 4

(Pin 7 for 14 Pin D Package)

Internal Clock

Output – Max. Duty Cycle

V - Pin 6

(Pin 10 for 14 Pin D Package)

V - Pin 4

(Pin 7 for 14 Pin D Package)

Internal Clock

Output – Max. Duty Cycle

V - Pin 6

(Pin 10 for 14 Pin D Package)

Oscillator timing capacitor CT is charged by VREF through RT and discharged by an

internal current source. During the discharge time, the internal clock signal blanks the

output to the low state. Selection of RT and CT therefore determines both oscillator

frequency and maximum duty cycle.

Charge and discharge times are determined by the formulae:

tc ≈ 0.55 RTCT

( ) td ≈ RTCT Rn

.0063 RT – 2.3

.0063 – 4

Resultant frequency

f

=

(tc

1

+

td)

For RT > 5kΩ,

Resultant frequency

f≈

1.8

(RTCT)

Semelab plc. Telephone (01455) 556565. Telex: 341927. Fax (01455) 552612.

Prelim. 2/95

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