PBL388121SOT 데이터 시트보기 (PDF) - Ericsson

부품명

상세내역

제조사

PBL388121SOT

Voice-switch circuit for Handsfree speakerphone TAM

Ericsson  

PBL 388 12

CTR 1

Txout 5

F3

4

PBL 388 12

Control

F6

12 Rxout

16 GND

13

6

11

V+ 15

+

F2

-Txin 2 -

+Txin

3

F1

+

8

N Det R5

7

TxDet

9

CMP

Ref.

10

RxDet

F5

F4 14 Rxin

+ C4

+

+

C3 C1 C2

Figure 5. Passive networks setting the speech control function.

PBL388 12

F2

100k 100k

F1 +

2

Tx

3 3k 3k

~ VTxin

I

Ref.

16

F5

120k 120k

F4

+

20k

14

Rx

~

VRxin

Figure 6. Receiver and transmitter channel input arrangement.

Functional Description

Speech control section

Transmitter and Receiver

Channels

The transmitter and receiver channels

consist of three amplifying stages each,

F1, F2, F3 and F4, F5, F6. The inputs of

the amplifiers must be ac. coupled

because they are dc. vise at the internal

reference voltage (≈2V) level. F1 and F4

are fixed gain amplifiers of 30,5 dB and

15.5 dB respectively, while the rest of them

are of controlled gain type.The gain of F2,

F3 as well as F5 and F6 is controlled by

comparators. The comparator receives its

information partly from the summing point

of the transmitter, receiver and backgro-

und noise detectors at CMP input and

partly through the control input, CTR,

which controls the gain dynamics (25 or

50 dB). Amplifiers F2 and F3 have the

maximum gain when the transmitter

channel is fully open, consequently the

amplifiers F5 and F6 will have minimum

gain and vice versa. See figure 5 and figure

11.

The positive input on transmitter and the

negative input on receiver channel has a

rather high input impedance. It renders a

good gain precision and noise

performance when used with low signal

source impedance. The differential input

of the transmitter channel can be used to

suppress unwanted signals in the

microphone supply, see figure 7. Also see

application 1.

Signal Detectors and

Comparator

The signal detectors sense and rectify

the receiver and microphone signals to

opposite polarities referenced to the

internal reference voltage of approx. 2V.

The voltage at RxDet will go positive and

at TxDet negative in the presence of a

signal at the respective channel input. In

the idle (no signal) state, the voltages at

RxDet ,TxDet and CMP are equal to the

internal reference voltage. Signal at Txin

will result in an decreasing level at

TxDetout and hence also at CMP input.

6

Share Link: