Philips Semiconductors

Product specification

SA5753

Audio processor – filter and control section

1997 Nov 07

5

AC ELECTRICAL CHARACTERISTICS (continued)

SYMBOL

PARAMETER

TEST CONDITIONS

LIMITS

UNIT

SYMBOL

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

TX overall gain

3kHz

8

9

9.6

dBm0

TX overall gain

5.9kHz

-52

-45

dBm0

TX BPF dynamic range

TBD

dB

f = 3kHz

100

k

Ω

Slew rate

0.75

V/

µs

Output impedance

f = 3kHz

40

Ω

Output swing (limiting)

1.2

Output swing (1% THD)

5k

Ω load (25

1.0

Tx DTMF signal with TXLPF and pre-emphasis

0.45

V/kHz

Rx DTMF sidetone

–0.8

5.2

dBm0

Time delay to mute from RX MUTE or TX MUTE

transition

0.5

0.5

µs

µs

Table 1. Gain Control Blocks (Bit 0 is Least Significant Bit)

SYMBOL

Bits

TYPICAL STEP (dB)

TYPICAL GAIN (dB)

SYMBOL

Bits

TYPICAL STEP (dB)

MIN

MAX

A1

4

–0.8

–12.0

0

A2a

5

±0.25

–3.75

+3.75

A2b

2

–6, (–12 on first)

–24.0

0

A3

4

–1.0

–17.0

–2.0

A4

4

±0.5

–3.5

+3.5

A6

4

–2.0

–30.0

0

A7

4

±0.5

–3.5

+3.5

NAMPS

1

+1.9 in A2b

–7.6 in A4

VCO

1

+6.0 in A4

For A2a, A4 and A7:

MSB sets the sign of the gain

MSB = 0 for gain

MSB = 1 for attenuation

For all Gain Blocks:

All bits set to 0 = 0dB gain

All bits set to 1 = maximum gain or attenuation

FUNCTIONAL DESCRIPTION

The SA5753 is an audio signal processor designed to meet the

requirements of compact low voltage radio telephone equipment. It

includes transmit and receive bandpass filters for voiceband

(300-3000Hz) with pre-emphasis and de-emphasis respectively, a

transmit peak deviation limiter, voice channel mute switches and a

interface is provided for software programmability of a DTMF

generator, mute polarity, selection of different power down and

operating modes and control of the gain in both the transmit and

receive channels.

Software programmable gain control allows the device to be

automatically optimized during equipment production and offers

flexibility during normal operation.

Gain Blocks

The programmable gain blocks are shown in Table 1 and Figure 2.

The purpose for each block is as follows:

a. A1 compensates for microphone gain variations in the transmit

path.

b. A2a compensates for transmitter dynamic range variations due to

manufacturing tolerances of the SA5753 and SA5752 compandor

companion device. To meet AMPS requirements, the dynamic

range between the zero crossing signal level of the compandor

and the peak signal allowed by the deviation limiter is adjusted to

12.34dB.

c. A2b allows coarse attenuation to be inserted in the transmit path

to eliminate positive feedback effects in hands-free speaker

applications. First step is 12dB followed by two steps of 6dB.

pin (Pin 20) and should be adjusted after A2a and A4 have been

previously optimized. The SA5753 will interface directly with the

UMA1000T data processor (which produces a 2Vpk data signal).

For NAMPS applications an additional 10 to 14dB resistive divider