L7581 AGERE | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 16
Technical content
Features
■ Small size/surface-mount packaging ■ Monolithic IC reliability ■ Low impulse noise ■ Make-before-break, break-before-make operation ■ Clean, bounce-free switching ■ Low, matched ON-resistance ■ Built-in current limiting, thermal shutdown, and SLIC protection ■ 5 V only operation, very low power consumption ■ Battery monitor, all OFF state upon loss of battery ■ No EMI ■ Latched logic level inputs, no drive circuitry ■ Only one external protector required
Applications
■ Central office ■ DLC ■ PBX ■ DAML ■ HFC/FITL
Description
The L7581 Ringing Access Switch is a monolithic solid-state device that provides the switching func- tionality of a 2 form C switch. The L7581 is designed to provide power ringing access to tip and ring in central office, digital loop carrier, private branch exchange, digitally added main line, and hybrid fiber coax/fiber-in-the-loop ana- log line card applications. The L7581 has three states: the idle talk state (line break switches closed, ringing access switches open), the power ringing state (line break switches open, ringing access switches closed), and an all OFF state. The L7581 offers break-before-make or make-before- break switching, with simple logic level input control. Because of the solid-state construction, voltage tran- sients generated when switching into an inductive ringing load during ring cadence or ring trip are mini- mized, possibly eliminating the need for external zero cross switching circuitry. State control is via logic level inputs, so no additional driver circuitry is required. The line break switch is a linear switch that has exceptionally low ON-resistance and an excellent ON-resistance matching characteristic. The ringing access switch has a breakdown voltage rating >480 V which is sufficiently high, with proper protec- tion, to prevent breakdown in the presence of a tran- sient fault condition (i.e., passing the transient on to the ringing generator). Incorporated into the L7581A xx is a diode bridge/ SCR clamping circuit, current-limiting circuitry, and a thermal shutdown mechanism to provide protection to the SLIC device and subsequent circuitry during fault conditions (see Figure 1). Positive and negative lightning is reduced by the current-limiting circuitry and steered to ground via diodes and the integrated SCR. Power cross is also reduced by the current- limiting and thermal shutdown circuits. The L7581B xx version provides only an integrated diode bridge along with current limiting and thermal shutdown, as shown in Figure 2. This will cause pos- itive faults to be directed to ground and negative faults to battery. In either polarity, faults are reduced by the current-limit and/or thermal shutdown mecha- nisms.
Table 1. Pin Descriptions erence for protection circuit. 2 4 NC No connection. 15 13 NC No connection. 32 T BA T Connect to TIP on SLIC side. 14 15 R BA T Connect to RING on SLIC side. 43 T LINE Connect to TIP on line side. 13 14 R LINE Connect to RING on line side.
56 T RINGING Connect to return ground for
12 12 R RINGING Connect to ringing generator. 7 5 NC No connection. 10 10 INPUT Logic level input switch control. in the thermal shutdown mode. extended periods can adversely affect device reliability. Table 2. Absolute Maximum Ratings Parameters susceptibility testing and protection design evaluation. here was obtained by using these circuit parameters. Table 3. HBM ESD Threshold Voltage
5 V Power Supply — 7 V
4 Lucent Technologies Inc. Data Sheet November 1999L7581 Ringing Access Switch
Electrical Characteristics
TA = –40 °C to +85 °C, unless otherwise specified. Minimum and maximum values are testing requirements. Typical values are characteristics of the device and are the result of engineering evaluations. T ypical values are for information purposes only and are not part of the test- ing requirements. Table 4. Power Supply Specifications this state until the battery voltage drops below –15 V . Table 5. Break Switches, 1 and 2
- This parameter is not tested in production. Choice of secondary protector should ensure this rating is not exceeded.
† Applied voltage is 100 Vp-p square wave at 100 Hz.
Table 6. Ring Return Switch, 3
- This parameter is not tested in production. Choice of secondary protector should ensure this rating is not exceeded.
† Applied voltage is 100 Vp-p square wave at 100 Hz. Table 7. Ringing Access Switch, 4 current to less than 2 mA nominally. Consult your Lucent T echnologies Microelectronics Group account executive for additional details. † Choice of secondary protector and series current-limit resistor should ensure these ratings are not exceeded. ‡ Applied voltage is 100 Vp-p square wave at 100 Hz.
Table 8. Additional Electrical Characteristics
- T emperature shutdown flag (TSD) will be high during normal operation and low during temperature shutdown state.
Line Card Access Switches Application Note. to the state of the line break contacts. ringing access switch contact is opened (or broken). switch contacts are closed (made).
- See the T ruth T able (Table 12) for an explanation of
designed to be safely away from the test limit of 80 mA. use a B series device (eliminates the SCR). Table 9. Make-Before-Break Operation Table 10. Break-Before-Make Operation
5 V 5 V/Float Power
0 V 5 V/Float Make-
from the ring node of the SLIC. waiting for zero current to turn off.
0 V 0 V All Off Zero current has occurred and
88 Lucent Technologies Inc. Data Sheet November 1999L7581 Ringing Access Switch Power Supplies Both the 5 V and battery supply are brought onto the L7581. The L7581 requires only the 5 V supply for switch operation; that is, state control is powered exclu- sively off of the 5 V supply. Because of this, the L7581 offers extremely low power dissipation, both in the idle and active states. The battery voltage is not used for switch state control. The battery is used as a reference voltage by the inte- grated secondary protection circuit. When the voltage at T BA T or RBA T drops 2 V to 4 V below the battery, the integrated SCR will trigger, thus preventing fault- induced overvoltage situations at the T BA T/RBA T nodes. Loss of Battery Voltage As an additional protection feature, the L7581 monitors the battery voltage. Upon loss of battery voltage, the L7581 will automatically enter an all OFF state and remain in that state until the battery voltage is restored. The L7581 is designed so that the device will enter the all OFF state if the battery rises above –10 V and will remain off until the battery drops below –15 V . Monitoring the battery for the automatic shutdown fea- ture will draw a small current from the battery, typically 4 µA. This will add slightly to the overall power dissipa- tion of the device. Impulse Noise Using the L7581 will minimize and possibly eliminate the contribution to the overall system impulse noise that is associated with ringing access switches. Because of this characteristic of the L7581, it may not be necessary to incorporate a zero cross switching scheme. This ultimately depends upon the characteris- tics of the individual system and is best evaluated at the board level. Protection Integrated SLIC Protection Diode Bridge/SCR In the L7581Axx version, protection to the SLIC device or other subsequent circuitry is provided by a combina- tion of current-limited break switches, a diode bridge/ SCR clamping circuit, and a thermal shutdown mecha- nism. In the L7581B xx version, protection to the SLIC device or other subsequent circuitry is provided by a combination of current-limited break switches, a diode bridge, and a thermal shutdown mechanism. In both versions, during a positive lightning event, fault current is directed to ground via steering diodes in the diode bridge. Voltage is clamped to a diode drop above ground. In the A version, negative lightning causes the SCR to conduct when the voltage goes 2 V to 4 V more negative than the battery, and fault currents are directed to ground via the SCR and steering diodes in the diode bridge. Note that for the SCR to foldback or crowbar, the ON voltage (see Table 10) of the SCR must be less nega- tive than the battery reference voltage. If the battery voltage is less negative than the SCR ON voltage, the SCR will conduct fault currents to ground; however, it will not crowbar. In the B version, negative lightning is directed to battery via steering diodes in the diode bridge. For power cross and power induction faults, in both ver- sions, the positive cycle of the fault is clamped a diode drop above ground and fault currents steered to ground. In the A version, the negative cycle will cause the SCR to trigger when the voltage exceeds the bat- tery reference voltage by 2 V to 4 V . When the SCR triggers, fault current is steered to ground. In the B ver- sion, the negative cycle of the power cross is steered to battery. Current Limiting During a lightning event, the current that is passed through the break switches and presented to the inte- grated protection circuit and subsequent circuitry is lim- ited by the dynamic current-limit response of the break switches (assuming idle/talk state). When the voltage seen at the T LINE/RLINE nodes is properly clamped by an external secondary protector, upon application of a
1000 V 10 x 1000 pulse (LSSGR lightning), the current
BA T/RBA T nodes will typically be a pulse of magnitude 2.5 A and duration less than 0.5 µs.
Lucent Technologies Inc. 9 Data Sheet November 1999 L7581 Ringing Access Switch Protection (continued) Integrated SLIC Protection (continued) During a power cross event, the current that is passed through the break switches and presented to the inte- grated protection circuit and subsequent circuitry is lim- ited by the dc current-limit response of the break switches (assuming idle/talk state). The dc current limit is specified over temperature between 100 mA and 250 mA. Note that the current-limit circuitry has a negative tem- perature coefficient. Thus, if the device is subjected to an extended power cross, the value of current seen at T BA T/RBA T will decrease as the device heats due to the fault current. If sufficient heating occurs, the tempera- ture shutdown mechanism will activate and the device will enter an all off mode. Temperature Shutdown Mechanism When the device temperature reaches a minimum of 110 °C, the thermal shutdown mechanism will activate and force the device into an all OFF state, regardless of the logic input pins. Pin T SD , when used as an output, will read 0 V when the device is in the thermal shut- down mode and +V DD during normal operation. During a lightning event, due to the relatively short duration, the thermal shutdown will not typically acti- vate. During an extended power cross, the device tempera- ture will rise and cause the device to enter the thermal shutdown mode. This forces an all off mode, and the current seen at T BA T/RBA T drops to zero. Once in the thermal shutdown mode, the device will cool and exit the thermal shutdown mode, thus reentering the state it was in prior to thermal shutdown. Current, limited to the dc current-limit value, will again begin to flow and device heating will begin again. This cycle of entering and exiting thermal shutdown will last as long as the power cross fault is present. The frequency of entering and exiting thermal shutdown will depend on the mag- nitude of the power cross. If the magnitude of the power cross is great enough, the external secondary protector may trigger shunting all current to ground. In the L7581, the thermal shutdown mechanism cannot be disabled by logic control at the T SD pin. The functionality of TSD differs from the L7541, L7582, and L7583. For the proper use of and understanding of any caveats related to T SD , please refer to the appropri- ate data sheet specifications. Electrical specifications relating to the overvoltage clamping circuit are outlined in Table 11. External Secondary Protector With the above integrated protection features, only one overvoltage secondary protection device on the loop side of the L7581 is required. The purpose of this device is to limit fault voltages seen by the L7581 so as not to exceed the breakdown voltage or input-output isolation rating of the device. T o minimize stress on the L7581, use of a foldback- or crowbar-type device is rec- ommended. A detailed explanation and design equa- tions on the choice of the external secondary protection device are given in the An Introduction to L758X Series of Line Card Access Switches Applica- tion Note. Basic design equations governing the choice of external secondary protector are given below: ■ |VBA Tmax| + |Vbreakovermax| < |Vbreakdownmin(break)| ■ |Vringingpeakmax| + |VBA Tmax| + |Vbreakovermax| < |Vbreakdownmin(ring)| ■ |Vringingpeakmax| + |VBA Tmax| < |Vbreakovermin| where: VBA Tmax—Maximum magnitude of battery voltage. Vbreakovermax—Maximum magnitude breakover voltage of external secondary protector. Vbreakovermin—Minimum magnitude breakover voltage of external secondary protector. Vbreakdownmin(break)—Minimum magnitude breakdown voltage of L7581 break switch. Vbreakdownmin(ring)—Minimum magnitude breakdown voltage of L7581 ring access switch. Vringingpeakmax—Maximum magnitude peak voltage of ringing signal. Series current-limiting fused resistors or PTCs should be chosen so as not to exceed the current rating of the external secondary protector. Refer to the manufac- turer’s data sheet for specifications.
Table 11. Electrical Specifications, Protection Circuitry that can flow into the battery before the SCR turns on. ‡ T wice ± dynamic current limit of break switches. § In some instances, the typical ON-state voltage can range as low as –25 V .
Figure 7. Typical RAS Application, A Version, Idle, or Talk State Shown Table 12. Truth Table
- Thermal shutdown mechanism is active with TSD floating or equal to 5 V .
- Forcing TSD to ground overrides the logic input pins and forces an all OFF state.
an internal node used for state control. INPUT , through the data latch to state control. Any changes in INPUT will be reflected in the state of the switches. as long as LA TCH is held high. state control via INPUT and LA TCH.
0 V 5 V/Float 1 On On Off Off 3
5 V 5 V/Float 1 Off Off On On 4
Lucent Technologies Inc. 13 Data Sheet November 1999 L7581 Ringing Access Switch Outline Diagrams 16-Pin, Plastic SOG (L7581AAE/BAE) Note:The dimensions in this outline diagram are intended for informational purposes only. For detailed schematics to assist your design efforts, please contact your Lucent Technologies Sales Representative. 5-4414r2 (C) Number of Pins (N) Maximum Length (L) Maximum Width Without Leads (B) Maximum Width Including Leads (W) Maximum Height Above Board (H) 16 10.49 7.62 10.64 2.67 W
0.610.51 MAX
H
0.28 MAX
0.10 SEATING PLANE
1.27 TYP
N L B PIN #1 IDENTIFIER ZONE
14 Lucent Technologies Inc. Data Sheet November 1999L7581 Ringing Access Switch Outline Diagrams (continued) 16-Pin, Plastic DIP (L7581AC/BC) Note:The dimensions in this outline diagram are intended for informational purposes only. For detailed schematics to assist your design efforts, please contact your Lucent T echnologies Sales Representative. 5-4410 (F) Number of Pins (N) Maximum Length (L) Maximum Width Without Leads (B) Maximum Width Including Leads (W) Maximum Height Above Board (H) 16 20.57 6.48 7.87 5.08 W H 0.58 MAX2.54 TYP
0.38 MIN
N PIN #1 IDENTIFIER ZONE L B
Lucent Technologies Inc. 15 Data Sheet November 1999 L7581 Ringing Access Switch
Ordering Information
*Devices on tape and reel must be ordered in 1000-piece increments. Device Part No. Description Package Comcode A TTL7581AAE Ringing Access Switch 16-Pin SOG 107338469 A TTL7581AAE-TR* Ringing Access Switch 16-Pin SOG (T ape & Reel) 107338493 A TTL7581AC Ringing Access Switch 16-Pin DIP 107338436 A TTL7581BAE Ringing Access Switch 16-Pin SOG 107392839 A TTL7581BAE-TR* Ringing Access Switch 16-Pin SOG (T ape & Reel) 107392953 A TTL7581BC Ringing Access Switch 16-Pin DIP 107392995
Lucent Technologies Inc. reserves the right to ma ke changes to the product(s) or inform ation contained herein without notice. No liability is assum ed as a result of their use or application. No rights under any patent accompa ny the sale of any such product(s) or inform ation. Co pyright © 1999 Lucent Technologies Inc. All Rights Reserved N ovember 1999 DS00 -050ALC (Replaces D S99-014ALC) For additional information, contact your M icroelectronics Group Account M anager or the following: IN TERNE T: http://www .lucent.com/micro E-M AIL: docm aster@mi cro.lucent.com N. AM ERICA : Microelectronics Group, Lucent Technologies Inc., 555 Union Boulevard, Room 30L-15P-BA, Allentown , PA 18103 1-800-372-2447, FAX 610-712-4106 (In C AN ADA: 1-800-553-2448, FAX 610-712-4106) ASIA PACIFIC : Microelectronics Group, Lucent Technologies Singapore Pte. Ltd., 77 Science Park Drive, #03-18 Cintech III, Singapore 118256 Tel. (65) 778 8833, FAX (65) 777 7495 C HIN A: M icroelectronics Group, Lucent Technologies (C hina) C o., Ltd., A-F2, 23/F, Zao Fong U niverse Building, 1800 Zhong Shan Xi Road, Shanghai 200233 P. R. C hina Tel. (86) 21 6440 0468, ext. 316, FAX (86) 21 6440 0652 JAPAN: M icroelectronics Group, Lucent Technologies Japan Ltd., 7-18, H igashi-G otanda 2-chom e, Shinagaw a-ku, Tokyo 141, Japan Tel. (81) 3 5421 1600, FAX (81) 3 5421 1700 EU R O PE : D ata Requests: M ICR O ELEC TR O N ICS GR OU P DATALIN E: Tel. (44) 7000 582 368, FAX (44) 1189 328 148 Technical Inquiries:GE R MA N Y: (49) 89 95086 0 (Munich), U N ITED KIN GDO M : (44) 1344 865 900 (Ascot), FR AN CE : (33) 1 40 83 68 00 (Paris), SWE D EN : (46) 8 594 607 00 (Stockholm), FIN LAND : (358) 9 4354 2800 (Helsinki), ITALY: (39) 02 6608131 (Milan), SPAIN : (34) 1 807 1441 (Madrid)