M62295GP Просмотр технического описания (PDF) - Renesas Electronics

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производитель

M62295GP

LCD Back-light Control IC

Renesas Electronics 

M62295GP

Function Description

• Output oscillation circuit and tooth-wave generating circuit for light control (RT, CT1, CT2)

RT (1.25 V)

CT1

CT2

R1

FB

Ro

CT1

CT2

R2

Figure 1 Connections of RT, CT1, CT2

As shown in Figure 1, charge/discharge current for each oscillation circuit is set by connecting resistors to RT

terminal.

RT terminal is connected to FB terminal by resistor to control the frequency for light control.

CT1 is the terminal for connecting capacitor for output oscillation circuit, generating triangular-wave oscillating

between lower limit (approx. 0.25 V) and upper limit (approx. 1.25 V) by the charge current set at RT terminal.

CT2 is the terminal for connecting capacitor for tooth-wave for light control, into which one twentieth of charge

current of CT1 terminal flows generating tooth-wave oscillating between lower limit (approx. 0.25 V) and upper

limit. (approx. 1.25 V)

Each charge current and oscillation frequency is decided by the formula shown below.

1.25

CT1 charge / Discharge current (ICT1 charge) =

Ro

1.25

1

CT2 charge / Discharge current (ICT2 charge) = Ro • 20

Output freq. (fOSC) =

1

T

1

=

2

CT1 • ICT1 charge

1

Tooth-wave freq. (CT2OSC) =

1

CT2 • ICT2 charge

Tooth-wave freq. (CT2OSC) (divided ratio) = CT1

Output freq. (fOSC)

CT2 • 10

CT1

G1

(POUT)

1.25 V

0.8 V

0.7 V

0.25 V

T

G2

(NOUT)

CT2

1.25 V

0.25 V

Figure 2 Waveform for CT1, CT2, and G1, G2

REJ03D0856-0201 Rev.2.01 Nov 14, 2007

Page 4 of 10

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