MT8889CP Zarlink Semiconductor, Inc., MT8889CP Datasheet - Page 6

• Manufacturer Part Number: MT8889CP
• Description: DTMF Transceiver, Integrated DTMF Transceiver with Adaptive Micro Interface
• Manufacturer: Zarlink Semiconductor, Inc.

Guard Time Adjustment
The simple steering circuit shown in Figure 5 is adequate for most applications. Component values are chosen
according to the following inequalities (see Figure 7):
V
St/GT
ESt
V
St/GT
ESt
DD
DD
V
DD
MT8889C
St/GT
V
ESt
Figure 6 - Guard Time Adjustment
t
DD
t
R1
Figure 5 - Basic Steering Circuit
REC
R1
REC
t
t
ID
DO
Zarlink Semiconductor Inc.
t
DAmax
t
t
t
DPmax
DAmin
DPmin
MT8889C
t
t
GTA
GTP
t
R1
t
GTP
GTP
R2
a) decreasing tGTP; (tGTP < tGTA)
b) decreasing tGTA; (tGTP > tGTA)
C1
R2
C1
+ t
= (R1C1) In (V
= (R1C1) In [V
+ t
+ t
+ t
= (R
= (R1C1) In [V
6
GTAmax
GTAmin
t
GTPmin
t
GTPmax
GTA
GTA
P
C1) In [V
R
R
Vc
= (R1C1) In (V
P
P
= (R
C1
= (R1R2) / (R1 + R2)
= (R1R2) / (R1 + R2)
- t
- t
- t
p
- t
C1) In (V
DD
DD
DPmin
DPmax
DAmax
DD
DD
DAmin
/ (V
/ V
/ (V
/ (V
TSt
DD
DD
DD
DD
DD
)
-V
-V
-V
/V
/V
TSt
TSt
TSt
TSt
TSt
)]
)]
)]
)
)
Data Sheet