Modes of Operation

MC44BS374T1/374T1A Advance Information

16 Modes of Operation

16.1 Power ON Settings

At power-ON, the MC44BS374T1/374T1A is configured as follows:

16.2 Power Supply

The three device Vccs (pins 10, 13 and 15) must be applied at the same time to ensure all internal blocks

are correctly biased. Do not bias any other pin before Vcc is applied to the MC44BS374T1/374T1A.

When all Vccs are switched to 0V, SDA and SCL pins are high impedance.

16.3 Standby modes

During standby mode, the modulator is switched to low power consumption. That is, the sound oscillator,

UHF oscillator, and the video and sound modulator section’s bias are internally turned OFF.

The MC44BS374T1/374T1A can be set to standby mode with a combination of 3 bits: OSC=0, SO=1 and

ATT=1

16.4 Transient Output Inhibit

To minimize the risk of interference to other channels while the UHF PLL is acquiring a lock on the

desired frequency, the Sound and Video modulators are turned OFF during a time out period for each of

the following two cases:

•

Power-ON from zero (i.e., all Vcc is switched from 0V to 5V).

•

UHF oscillator power-ON from OFF state (i.e., OSC bit is switched from 1 to 0)

There is a time-out of 263ms until the output is enabled. This lets the UHF PLL settle to its programmed

frequency. During the 263ms time-out, the sound PLL current source is set to 10

µA typical to speed up the

locking time. After the 263ms time-out, the current source is switched to 1

µA. Use care when selecting

loop filter components, to ensure the loop transient does not exceed this delay.

Table 8. Power ON Settings

WRITE MODE

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

ACK

C1-High Order Bits

1

0

0

0

0

0

0

0

ACK

C0-Low Order Bits

0

1

0

0

1

0

0

0

ACK

FM-High Order Bits

0

0

N11

N10

N9

N8

N7

N6

ACK

FL-Low Order Bits

N5

N4

N3

N2

N1

N0

0

0

ACK

Note:

N0 to N11 are set to have UHF oscillator on channel 71 (871.25MHz).

Note:

Peak White Clip is ON.

Note:

Sound frequency is 5.5MHz.

Note:

Logic Output Port is low voltage

Note:

Picture to sound ratio is 12dB.

Freescale Semiconductor, Inc.

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