w925e625 ETC-unknow, w925e625 Datasheet - Page 55

• Manufacturer Part Number: w925e625
• Description: 8-bit Cid Microcontroller
• Manufacturer: ETC-unknow

Ring Detector
The application circuit in Figure 6-18 illustrates the relationship between the RNGDI, RNGRC and
RNG signals. The combination of RNGDI and RNGRC is used to detect an increase of the RNGDI
voltage from ground to a level above the Schmitt trigger high going threshold voltage V
The RC time constant of the RNGRC pin is used to delayed the output pulse of the RNG flag for a low
going edge on RNGDI. This edge goes from above the V
threshold voltage V
signal, to ensures a minimum RNG high interval and to filter the ring signal to get an envelope output.
The rising signal of RNG will set the bit RNGF(CIDFG.0) high to cause the CID flag(CIDF) high.
The diode bridge shown in Figure 6-18 works for both single ended ring signal and balanced ringing.
The R1 and R2 are used to set the maximum loading and must be of equal value to achieve balanced
loading at both the tip and ring line. R1, R3 and R4 form a resistor divider to supply a reduced voltage
to the RNGDI input. The attenuation value is determined by the detection of minimal ring voltage and
maximum noise tolerance between tip/ring and ground.
Tip/A
Ring/B
Time constant is:
T = R5 C3 ln [VDD / (VDD - V
V
Allowance minimal ring voltage (peak to peak) is:
Vpp
Tolerance to noise between Tip and Ring and VSS is:
Vpeak
T+(min)
(max ring)
(max noise)
<= V
= 2 (V
T+
C1=0.1uF
C1=0.1uF
<= V
= V
T+(max)
T+(min)
T+(max)
T-
. The RC time constant must be greater than the maximum period of the ring
(R1 + R3 + R4) / R4 + 0.7)
R2=470K
(R1 + R3 + R4) / R4 + 0.7
R1=470K
T+
)]
Figure 6-18 Application Circuit of the Ring Detector
R3=200K
- 55 -
R5=150K
C3=0.22uF
R4=300K
T+
voltage to the Schmitt trigger low going
R5 from 10K ohm to 500K ohm.
C3 from 47 nF to 0.68 uF.
RNGRC
RNGDI
Publication Release Date: July 4, 2005
W925E/C625
T+
.
Revision A10
RNG