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ISL5571A 数据表(PDF) 7 Page - Intersil Corporation |
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ISL5571A 数据表(HTML) 7 Page - Intersil Corporation |
7 / 12 page 7 Circuit Operation and Design Information Introduction The ISL5571A was designed to be used in subscriber line card applications. A typical application circuit is shown in Figure 1. Its main purpose is to momentarily disconnect the voice circuit (SLIC and CODEC) and connect an external ring generator to ring the phone. This function has been traditionally done by electromechanical relays. The ISL5571A offers the system designer a solid-state switching solution with distinct advantages over the electromechanical relay. These advantages are as follows: • Lower power consumption (20mW vs. 150mW for the relay) • Smaller size, surface mounted package • Bounce-Free switching • Lower impulse noise, Low EMI • Longer life • Provides current limiting, thermal shutdown, and over- voltage protection for the SLIC and CODEC Their bounce-free operation, long lifetime, small size, and low power consumption make the solid-state access switch the preferred choice over electromechanical relays whenever board area, high reliability, and heat reduction are primary concerns. The ISL5571A was designed to be a drop in replacement for the Lucent ATTL7581AAE LCAS device. The Intersil ISL5571A offers superior rON matching between the line break switches for optimal longitudinal balance, higher temperature operation (enabling continuous operation in short loop, high Ringer Equivalency Number applications) and with 3V TTL logic controlled inputs. Basic Functional Description This section describes the basic operation of the ISL5571A. From the application circuit shown in Figure 1, the ISL5571A consists of four switches, the Line Break switches (SW1, SW2), the Ring Return switch (SW3), and the Ring Access switch (SW4). The Line Break switches (SW1 and SW2) open and close in unison to connect and disconnect the voice / data signal from the phone. The Ring Access switch and the Ring Return switch (SW3 and SW4) open and close in unison, to connect and disconnect the external ring generator to the phone. The ISL5571A has three possible operating states: the Idle / Talk state, the Power Ringing state, and the All OFF state. It also has a built in Logic State Latch. The Logic State Latch enables the user to latch the logic state of the ISL5571A in either the Idle / Talk state or the Power Ringing state. The three control logic pins for the ISL5571A are the INPUT pin, the TSD pin and the LATCH pin. These logic pins are controlled by TTL logic levels (0V - 0.8V for logic low and 2.4V - 5.0V for logic high). The combination of the logic levels applied at these pins determine which of the three logic states the device will be in and whether the Logic State Latch is active. The truth table for the ISL5571A is shown in Table 9. A description of each operating state and the control logic pins follows: TABLE 9. TRUTH TABLE - ISL5571A LOGIC STATE LOGIC INPUTS SWITCH CONDITION LATCH INPUT TSD TIP LINE BREAK SWITCH RING LINE BREAK SWITCH RINGING RETURN SWITCH RING ACCESS SWITCH IDLE / TALK 0 0 1 or Floating (Note 11) ON ON OFF OFF POWER RINGING 0 1 1 or Floating (Note 11) OFF OFF ON ON IDLE / TALK LATCHED (Note 12) 1 0 1 or Floating (Note 11) ON ON OFF OFF POWER RINGING LATCHED (Note 12) 1 1 1 or Floating (Note 11) OFF OFF ON ON All OFF X X 0 (Note 13) OFF OFF OFF OFF NOTES: 11. Thermal shutdown mechanism is active with TSD floating or equal to 5V. 12. If the LATCH pin is low, the logic state of the device is controlled by the INPUT pin. When the LATCH pin goes high, the current logic state is latched. As long as the LATCH pin is held high, the device will no longer respond to any changes applied to the INPUT control pin. The state of the device will be permanently latched until the LATCH pin is taken low. 13. Setting TSD to a logic low overrides the LATCH and INPUT logic pins and forces all switches to turn OFF. ISL5571A |
类似零件编号 - ISL5571A_04 |
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类似说明 - ISL5571A_04 |
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