SG1842F View Datasheet(PDF) - Microsemi Corporation

Part Name

Description

Manufacturer

SG1842F

Current Mode PWM Controller

Microsemi Corporation 

Application Information

Application Information

The oscillator of the 1842/43 family of PWM's is designed such that many values of RT and CT will give the

same oscillator frequency, but only one combination will yield a specific duty cycle at a given frequency.

Given:

Frequency ≡ f

Maximum Duty Cycle ≡ Dm

Calculate: RT = 267 �(1.7(61).7( 61−)1D/mDm)/D−m1 −1� (Ω)

where 0.3 < Dm < 0.95

CT

=

1.86 ∗ Dm

f ∗ RT

(µF)

For Duty-Cycles above 95% use:

VREF

RT

RT /CT

CT

GND

F ≈ 1.86 Where RT ≥ 5kΩ

RTCT

Figure 15 · Oscillator Timing Circuit

11

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