Bell 202 and V.23 Compatible Modem
Rx Energy Detector
‘Off’ to 'On' Threshold Level
Hysteresis (measured at VDD = 3.0V
and VDD = 5.0V)
'Off' to 'On' Time (Figure 8 TeON):
1200bps Rx mode
75/150bps Rx mode
Call Progress Detect mode
'On' to 'Off' Time (Figure 8 TeOFF):
1200bps Rx mode
75/150bps Rx mode
Call Progress Detect mode
XTAL/CLOCK Input
'High' Pulse Width
'Low' Pulse Width
22
Notes
6, 10
6, 10
6, 10
Min.
-48.0
2.0
6, 10
8.0
20
20
11
100
11
100
CMX624 Preliminary Information
Typ.
Max.
Unit
-43.0
dBm
dB
25
ms
48
ms
48
ms
ms
ms
ms
ns
ns
Notes:
1. At 25°C, not including any current drawn from the CMX624 pins by external circuitry other than X1, C1,
and C2.
2. All logic inputs at VSS except for RT and CS inputs, which are at VDD.
3. Excluding RD, RT and XTAL/CLOCK pins.
4. At VDD = 5.0V, Tx output level control bit set to ‘1’; load resistance greater than 40kΩ.
5. For each of the TX- (if enabled) and TX+ pins, load between pin and VDD/2.
6. Measured at the Rx Input Amplifier output (pin RXAMPOUT) for VDD = 5.0V.
The internal threshold levels are proportional to VDD. To cater for other supply voltages or different signal
level ranges the voltage gain of the Rx Input Amplifier should be adjusted by selecting the appropriate
external components as described in Section 5.1.
7. Flat noise in 300-3400 Hz band for V.23, 200-3400 Hz for Bell 202.
8. Set by Rx UART and Xtal frequency.
9. 2100Hz detection requires a signal within the amplitude range given in Section 4.5.
10. Measured with 1300Hz signal in 1200bps mode, 390Hz for 75bps or 150bps and Call Progress mode,
signal level -33dBm for time delay measurements.
11. Timing for an external input to the XTAL/CLOCK pin.
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