APW7078XI-TR Просмотр технического описания (PDF) - Anpec Electronics

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производитель

APW7078XI-TR

Single PWM Switching Controller

Anpec Electronics 

APW7078

Typical Characteristics

(TA = 25°C, VDD = 3.3V, unless otherwise specified)

Frequency Variation Ratio vs. Supply Voltage

10

8

6

4

2

0

-2

-4

-6

-8

-10

1

TA=25°C

RT=3.3k Ω

CT=270pF

2

3

4

5

Supply Voltage(V)

Frequency Variation Ratio vs. Temperature

5

CT=270pF

4

RT=3.3kΩ

3

2

1

0

-1

-2

-3

-4

-5

-40 -20

0

20

40

60

80

Temperature(°C)

Function Description

Setting Oscillating Frequency

The oscillator circuit generat e a triangular sawt ooth

wave with a peak of 0.9V and through of 0.16V using

the timing capacitor(Ct) and the timing resistor(Rt) that

are connected to OSC pin. This oscillator can provide

oscillating frequency up to 1MHz.

Vosc

VH

0.9V

i = c ∆V

∆t

t1

=

Ct

⋅

0.9V − 0.16V

2mA

= 370 ⋅ C t

−t

V(t) = VH ⋅ e RtCt

t2 = RtCt ln(VH / VL ) = 1.72 ⋅ RtCt

T = t1 + t2 = Ct (370 +1.72Rt )

Setting Output Voltage

V(t)

VL

t

The out put voltage is set using t he INV pin and a re-

sistor divider connected to the output as shown in the

typical operating circuit. The internal reference volt-

0.16V age is 0.5V with 2% variation, so the ratio of the feed-

t1

t2

bac k res istors set s the output voltage according to

Time the following equation:

C opyright © ANPEC Electronics C orp.

9

Rev. A.3 - Nov., 2005

www.anpec.com.tw

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