TEA2029 데이터 시트보기 (PDF) - STMicroelectronics

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TEA2029

APPLICATION NOTE

STMicroelectronics 

TEA2028 - TEA2029 APPLICATION NOTE

Figure 32

VIDEO

ON PIN 27

LINE SYNC .

ϕ1 SIGNAL

0.3µs

2 .35µs 2.35µs

L I NE

INHIBITI ON Inhibit ion

5.8µs

6.5µs

In hib it io n

Figure 33 : ϕ1 Inhibition Logic Block Diagram

Video Recognition

FRI

Mute

LS

ϕ1

FS

≥1

Line Inhibition

BLK

&

VCR

&

SINH(L)

&

Line Sync.

&

&

S INH(S)

500µA

(Long)

100µA

(short)

Phase Comparator (ϕ1)

V.4 - Line saw-tooth generator

Before going through a detailedstudy of the second

phase locked loop ”φ2”, let’s have an overview of

the linesaw-tooth generator which has been mainly

implemented for φ2 phase variations and also the

phase modulation of the switching power supply.

It uses the combination of an external capacitor

connected to Pin 13 and an internally implemented

constant current generatorto generatea saw-tooth

voltage at line frequency.

Its frequency is determined by the reset frequency

Figure 34

of the capacitor ”C13”. This reset signal is issued

by the line logic circuitry at a period multiple of VCO

period (×32).

-

IC

=

K

⋅

IR

=

K

⋅

1.26

R14

=

200µA

-

V13PP

=

IC

(TH − treset)

C13

=

K

⋅

1.26 (TH − treset)

R14 ⋅ C13

= 3.48V

- VCE(SAT)T1 ≈ 20mV ⇒ V13(MAX) = 3.5V

- In sync mode :

TH = 64µs, tRESET = 6.5µs, K = 0.527 ± 2%

+

VCC

IR

xK

IC

V13

TH

x1

To ϕ2

3.5 VPP

64µs

and SMPS

0

t

14

13

Constant

1.26V

IR

R14

3.32kΩ

T1

C13

3.3nF

Reset

Reset

t

6.5µs

18/46

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