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MH88400-2 Datasheet(PDF) 7 Page - Mitel Networks Corporation |
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MH88400-2 Datasheet(HTML) 7 Page - Mitel Networks Corporation |
7 / 10 page 2-17 Preliminary Information MH88400 TIP RLS TF TXIN RING VX VR RVLC LC AGND VDD TIP RING C2 C1 +5V 1 2 3 4 6 7 9 10 11 13 14 D1 Audio Output Audio Input Ring Voltage & Loop Current Detect Output Loop Control Input MH88400 NOTES: Calls are set up and cleared in this mode by the external controller. It turns on the loop via Loop Control, dialling by pulsing loop control (or via DTMF tones) and clearing down by turning Loop Control off. 1) C1: 10 µF, 6V Tantalum 2) C2: 0.1 µF, 250V (Typical Value) 3) D1: 180VDC Foldback Diode, e.g. TISP4180, TISP5180 4) VX and VR are biased at 2.5V, therefore, coupling capacitors may be required depending on application. + R1 5) VX and VR are biased at 2.5V, therefore, coupling capacitors may be required depending on application. Figure 3 - Typical Application Circuit However, by adding external resistors to the VX output, the Transmit Gain can be reduced as shown in Figure 5. To limit the output current drawn, the minimum recommended resistance to ground is 2k Ω. TIP-RING Drive Circuit The audio input ground (AGND) referenced signal at VR, biased at 2.5V, is converted to a balanced output signal at Tip-Ring. 2-4 wire isolation is achieved through optical isolation. The LC input is activated, low, and loop current must be flowing. TIP-RING Receive Circuit The differential audio signal at Tip-Ring is converted to a ground (AGND) referenced signal, biased at 2.5V, at the VX output. 2-4 Wire isolation is achieved through a combination of optical isolation and transformerler isolation. The receive circuit operated with or without loop current and LC can be either high or low. Signal reception with no loop current can be used for on-hook reception of, for example, caller identification signals. Transmit Gain Transmit Gain (Tip-Ring to VX) is fixed as indicated in “AC Electrical Characteristics”. Overall Transmit Gain = -0.4 dB + 20log (R4 / (R4 + R3)) The output impedance of the VX output is about 5 Ω, therefore, with two external 1k Ω resistors configured as per Figure 5, this will result in 6dB of attenuation for a total gain of -6.4dB. For correct gain, the MH88400 input impedance must match the line impedance. Receive Gain Receive Gain (VR to Tip-Ring) is fixed as indicated in “AC Electrical Characteristics”. However, by adding a single external resistor in series with the VR input, the Receive Gain can be reduced. Overall Receive Gain = 3.5dB + 20log (47k Ω /(47kΩ + Rext), The input impedance of the VR input is 47k Ω, therefore, an external 100k Ω resistor in series with this input will result in 9.9dB of attenuation for a total gain of -6.4dB. For correct gain, the MH88400 input impedance must match the line impedance. |
Similar Part No. - MH88400-2 |
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Similar Description - MH88400-2 |
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