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T4091N-DDB Datasheet(PDF) 6 Page - ATMEL Corporation |
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T4091N-DDB Datasheet(HTML) 6 Page - ATMEL Corporation |
6 / 38 page 6 U4091BM-N 4666B–CORD–08/04 DC Line Interface and Supply-voltage Generation The DC line interface consists of an electronic inductance and a dual-port output stage which charges the capacitors at VMPS and VB. The value of the equivalent inductance is given by: The U4091BM-N contains two identical series regulators which provide a supply voltage VMP of 3.3 V suitable for a microprocessor. In speech mode, both regulators are active because VMPS and VB are charged simultaneously by the DC line interface. The output current is 6 mA. The capacitor at VMPS is used to provide the microcomputer with suffi- cient power during long line interruptions. Thus, long flash pulses can be bridged or an LCD display can be turned on for more than 2 seconds after going on-hook. When the system is in ringing mode, VB is charged by the on-chip ringing power converter. In this mode, only one regulator is used to supply VMP with maximum 3 mA. Supply Structure of the Chip A main benefit of the U4091BM is the easy implementation of various applications due to the flexible system structure of the chip. Possible applications: • Group listening phone • Hands-free phone • Phones which feature ringing with the built-in speaker amplifier • Answering machine with external supply The special supply topology for the various functional blocks is illustrated in Figure 4 on page 7. There are four major supply states: 1. Speech condition: In speech condition, the system is supplied by the line current. If the LIDET-block detects a line voltage above approximately 2 V, the internal signal VLON is acti- vated. This is detected via the serial bus, all the blocks which are needed have to be switched on via the serial bus. For line voltages below 2 V, the switches remain in quiescent state as shown in the diagram. 2. Power down (pulse dialing): When the chip is in power-down mode (Bit LOMAKE), e.g., during pulse dialing, all internal blocks are disabled via the serial bus. In this condition, the voltage regulators and their internal band gap are the only active blocks. 39 MICO Microphone preamplifier output 40 AMPB Input for playback signal of answering machine 41 AMREC Output for recording signal of answering machine 42 STO Output for connecting the sidetone network 43 STC Input for sidetone network 44 STRC Input for sidetone network Pin Description Pin Symbol Function Note: 1. The protection device at Pin RECIN is disconnected. L 2R SENSE × C IND R DC R 30 × () × × R DC R 30 + () ------------------------------------------------------------------------------------------- = |
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