U4082B-DEV-BOARD Atmel, U4082B-DEV-BOARD Datasheet - Page 22

• Manufacturer Part Number: U4082B-DEV-BOARD
• Description: WiFi / 802.11 Modules & Development Tools Voice Switched Circuit
• Manufacturer: Atmel

8.2
22
Design Equations
U4082B
The above switching times occur, however, after the level detectors have detected the appropri-
ate signal levels, since their outputs operate the attenuator control block. Referring to
on page
(approximately 1 ms), determined by the internal 350 resistor and the external capacitor (typi-
cally 2 µF). The output's decay time is determined by the external capacitor and an internal 4 µA
current source, giving a decay rate of 60 ms for a 120 mV excursion at RLO or TLO. Total
response time of the circuit is not constant since it depends on the relative strength of the sig-
nals at the different level detectors and the timing of the signals with respect to each other. The
capacitors at the four outputs (RLO1, RLO2, TLO1, TLO2) must be of equal value (±10%) to
prevent problems in timing and level response.
The rise time of the level detector's outputs is not significant since it is so short. The decay time,
however, provides a significant part of the “hold time” necessary to hold the circuit during the
normal pauses in speech.
The components at the inputs of the level detectors (RLI1, RLI2, TLI1, TLI2) do not affect the
switching time but rather affect the relative signal levels required to switch the circuit and the fre-
quency response of the detectors.
The following definitions are used at 1 kHz with reference to
on page 23
Figure 8-1.
• G
• G
• G
• G
(typically 35V/V, or 31 dB)
(typically 10.2V/V, or 20.1 dB)
network (measured at 0.4V/V, or –8 dB)
MA
T
HA
HT
is the gain of the transmit attenuator, measured from TI to TO
is the gain from HTO–/HTO+ to Tip/Ring for transmit signals, and includes the balance
is the gain of hybrid amplifiers, measured from TO to the HTO–/HTO+ differential output
is the gain of the microphone amplifier measured from the microphone output to TI
6, the rise time of the level detectors' outputs to new speech is quick by comparison
where coupling capacitors are omitted for the sake of simplicity:
V
B
Power Supply Rejection of the Microphone and Hybrid Amplifiers
100
80
60
40
20
0
0.3
f (kHz)
HTO-, C
1
VB
C
= 1000 µF
VB
= 220 µF
MICO,
= 1000 µF
= 220 µF
Figure 1-2 on page 2
2
3
4743D–CORD–03/06
and
Figure 3-2
Figure 8-3