intersil ISL5571A DATA SHEET

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ISL5571A

Data Sheet July 2004

Access High Voltage Switch

The ISL5571A is a solid state device designed to replace the electromechanical relay used on Subscriber Line Cards. The device contains two Line Break MOSFET switches, one Ring Return MOSFET switch and one Ring Access SCR switch.

The ISL5571A is pin-for-pin compatible with the Lucent L7581AAE LCAS and Clare CPCL7581A Products. Improvements include: line break switches r

match (0.5Ω

Max) higher dV/dt sensitivity (5000V/µs), protection SCR hold current set to 110mA.

The line break MOSFETs have very low on resistance (<16.0Ω Typ) and Ron match (<0.05Ω Typ, 0.5Ω Max) and a blocking voltage >330V. The Ring Return MOSFET has a typical Ron of 50Ω and a blocking voltage >330V. The Ringing Access switch is implemented with a SCR device with a blocking voltage >480V. The SCR switch inherently offers low EMI connect and disconnect circuitry. All control I/Os use TTL thresholds making the device compatible with 3V logic.

The ISL5571A also includes on-chip protection in the form of an over-voltage clamping circuit, current-limited MOSFET switches, and thermal shutdown circuitry. The over-voltage clamping circuit consists of a diode bridge and SCR.

Ordering Information

PART

NUMBER

ISL5571AIB Yes -40 to 85 16 Ld SOIC M16.3 ISL5571AIBZ

(Note)

NOTE: Intersil Pb-free products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which is compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J Std-020B.

Add “-T” for tape and reel.

PROT

SCR

Yes -40 to 85 16 Ld SOIC

TEMP

RANGE (°C)

PACKAGE

TYPE

(Pb-free)

PKG.

DWG. #

M16.3

FN4920.5

Features

• Small Size/Surface-Mount Packaging

• Low Impulse Noise, Low EMI

• Clean, Bounce-Free Switching

• Line Break Switches

-0.5Ω Max r

-28Ω Max r

Match

• Built-In Current Limiting, Thermal Shutdown and Secondary Protection for the SLIC

• Optimized for Short Loop High REN Applications

• 3V/5V Logic-Capable I/O

• Pb-free Available

Applications

• Central Office

• PBX

•DLC

•HFC

•FITL

•DAML

Related Literature

• Technical Brief TB363 “Guidelines for Handling and Processing Moisture Sensitive Surface Mount Devices (SMDs)”

• Technical Brief TB379 “Thermal Characterization of Packages for ICs”

• Texas Instruments TISPL758LF3D Data Sheet

• Teccor Electronics Document DO-214AA

Pinout

ISL5571A

TOP VIEW

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

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| Intersil (and design) is a registered trademark of Intersil Americas Inc.

All other trademarks mentioned are the property of their respective owners.

F T

GND

BAT

LINE

NC NC

RING

16 15 14 13 12 11 10

BAT

LINE

NC R

RING

LATCH INPUT D

GND

1 2 3 4 5 6 7 8

Block Diagram

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LINE

RING

RETURN

SW3

RING ACCESS SW4

ISL5571A

ISL5571A - 16 LEAD SOIC

LINE BREAK

SW1

LINE BREAK

SW2

CONTROL LOGIC

BAT

SCR

BAT

GND

BAT

12 11 10 8

RING

INPUTLATCH

GND

TSD

ISL5571A

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Absolute Maximum Ratings T

Maximum Supply Voltages

) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-0.5V to +7V

) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-19V to -100V

BAT

ESD Rating (Human Body Model). . . . . . . . . . . . . . . . . . . . . . .500V

Die Characteristics

Substrate Potential. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V

Process . . . . . . . . . . . . . . . . . . . . . . . .6-inch BIMOS Bonded Wafer

CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.

NOTE:

is measured with the component mounted on a low effective thermal conductivity test board in free air. See Tech Brief TB379 for details.

1. θ

Electrical Specifications T

PARAMETER TEST CONDITION MEASURE MIN TYP MAX UNITS

OFF-State Leakage Current:

ON-Resistance:

ON-Resistance Match Per ON-resistance Test Condition of SW1, SW2 Magnitude

ON-State Voltage (Note 2) Break Switches in ON-State; I

DC Current Limit:

Dynamic Current Limit (t = <0.5µs)

Isolation:

dV/dt Sensitivity (Note 3) - 5000 - V/µs

NOTES:

2. Choice of secondary protection should ensure this rating is not exceeded.

3. Applied voltage is 100V

-40°C

25°C

85°C

-40°C 25°C 85°C

-40°C

25°C

85°C

V V V V V V

T T T

50/60Hz

V V V

Break Switches in ON-state; Ringing Access Switches OFF; Apply ±1000V at 10/1000µs Pulse; Appropriate External Secondary Protection in Place

V Logic Inputs = GND V Logic Inputs = GND V Logic Inputs = GND

square wave at 100Hz.

P-P

= 25°C Thermal Information

Thermal Resistance (Typical, Note 1) θ

SOIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Maximum Junction Temperature Plastic . . . . . . . . . . . . . . . . .150

Maximum Storage Temperature Range . . . . . . . . . -65

Maximum Lead Temperature (Soldering 10s). . . . . . . . . . . . .300

(SOIC - Lead Tips Only)

BAT

= -40°C to 85°C, Unless Otherwise Specified

TABLE 1. BREAK SWITCHES - ISL5571A - SW1, SW2

SWITCH

∆V

SW1 - rON SW2

SWITCH

SWITCH (DIFFERENTIAL) SWITCH (DIFFERENTIAL) SWITCH (DIFFERENTIAL) SWITCH (DIFFERENTIAL) SWITCH (DIFFERENTIAL) SWITCH (DIFFERENTIAL)

= ±10mA, ±40mA, T

LINE

= ±10mA, ±40mA, T

LINE

= ±10mA, ±40mA, T

LINE

SWITCH (ON) SWITCH (ON) SWITCH (ON)

SWITCH

= ±10V = ±10V = ±10V

(Both Poles) = ±310V

(Both Poles) = ±320V

(Both Poles) = ±330V

= -310V to GND = -60V to +250V = -320V to GND = -60V to +260V = -330V to GND = -60V to +270V

= -2V

BAT

= -2V

BAT

= -2V

BAT

= I

switch

LIMIT

(°C/W)

°C to 150°C

- - 220 V

-1.52.0A

12 16

0.05 0.5 Ω

125

250

µA

Peak

mA mA

µA

Ω Ω Ω

°C °C

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TABLE 2. RING RETURN SWITCH - ISL5571A - SW3

UNIT

PARAMETER TEST CONDITION MEASURE MIN TYP MAX

OFF-State Leakage Current:

-40°C

25°C

85°C

SWITCH (DIFFERENTIAL)

= -310V to GND = -60V to +250V = -320V to GND = -60V to +260V = -330V to GND = -60V to +270V

SWITCH

DC Current Limit

-40°C V 25°C V 85°C

Dynamic Current Limit (t = <0.5µs)

SWITCH (ON) SWITCH (ON)

SWITCH (ON) I

Break Switches in OFF-State; Ringing Access Switches ON; Apply ±1000V at 10/1000µs Pulse; Appropriate External

SWITCH

SWITCH SWITCH

SWITCH

Secondary Protection in Place ON-Resistance T ON-State Voltage (Note 4) Ring Return Switch in ON-State; I

= 0, ±10mA ∆V

LINE

= I

switch

at 50/60Hz V

LIMIT

Isolation:

-40°C

25°C

85°C

Logic Inputs = GND

(Both Poles) = ±310V

SWITCH

(Both Poles) = ±320V

SWITCH

(Both Poles) = ±330V

SWITCH

dV/dt Sensitivity (Note 5) - 5000 - V/µs

NOTES:

4. Choice of secondary protection should ensure this rating is not exceeded.

5. Applied voltage is 100V

square wave at 100Hz.

P-P

- - 350 mA

-200-mA

120 - - mA

-1.52.0A

- - 100 Ω

- - 130 V

Peak

µA

TABLE 3. RING ACCESS SWITCH - ISL5571A - SW4

PARAMETER TEST CONDITION MEASURE MIN TYP MAX UNITS

OFF-State Leakage Current:

-40°C

25°C

85°C

ON-Resistance I ON Voltage I Ring Access Switch Quiescent

Current During Ringing

SWITCH (DIFFERENTIAL)

SWITCH (DIFFERENTIAL) SWITCH (ON) SWITCH

= 5V, Ring Access Switches On, All Other

= ±70mA, ±80mA ∆V

(ON) = ±1mA V

= -245V to +210V = +245V to -210V = -255V to +210V = +255V to -210V = -270V to +210V = +270V to -210V

Switches Off

SWITCH

RING QUIESCENT

(Note 6)

µA

--12 Ω

--3V

-2.0-mA

Steady State Current (Note 7) --150mA Surge Current (Note 7) Ring Access Switch On, Time Duration = 100µs--2A Release Current 200 - 1000 µA Isolation:

-40°C

SWITCH

(Both Poles) = ±310V

SWITCH

µA

Logic Inputs = GND

25°C

85°C

V Logic Inputs = GND V Logic Inputs = GND

(Both Poles) = ±320V

SWITCH

(Both Poles) = ±330V

SWITCH

µA

dV/dt Sensitivity (Note 8) - 5000 - V/µs

NOTES:

6. Magnitude of the ring generator current not supplied to the ring load. I

7. Choice of secondary protector and series current-limit resistor should ensure these ratings are not exceeded.

8. Applied voltage is 100V

square wave at 100Hz.

P-P

RING QUIESCENT

= I

RING GEN

- I

RING LOAD

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TABLE 4. LOGIC I/O ELECTRICAL CHARACTERISTICS - ISL5571A

PARAMETER TEST CONDITION MEASURE MIN TYP MAX UNITS

Digital Input Characteristics:

Input Low Voltage Input High Voltage Input Leakage Current (High) Input Leakage Current (Low)

PARAMETER TEST CONDITION MEASURE MIN TYP MAX UNITS

Power Requirements:

Power Dissipation

Current

BAT

Temp. Shutdown Requirements (Note 9)

Shutdown Activation Temperature Shutdown Circuit Hysteresis

NOTE:

9. The Temperature Shutdown logic pin (TSD) will be high during normal operation and low during temperature shutdown state.

= 5.5V, V

TABLE 5. LOGIC I/O POWER REQUIREMENTS - ISL5571A

Idle/Talk State All OFF-State Ringing State V

BAT

Idle/Talk State All OFF-State Ringing State

= -75V, V

BAT

= -75V, V

BAT

= 5.5V, V

= 5.5V,

= -48V,

BAT

LOGIC-IN LOGIC-IN

= -48V,

= 5V = 0V

LOGIC-IN

IDD, I I

BAT

, I

BAT BAT

2.4

115712514135

6.6

8.8

11.0

1.2

1.6

2.0

1.0

0.8

1 1

8.5

11.5

18.2

2.0

2.1

3.3

10 10 10

V V

µA µA

mW mW mW

mA mA mA

µA µA µA

°C °C

TABLE 6. ELECTRICAL SPECIFICATION - PROTECTION CIRCUITRY - ISL5571A

PARAMETER TEST CONDITION MEASURE MIN TYP MAX UNITS

PARAMETERS RELATED TO DIODES

Voltage Drop at Continuous Current (50Hz/60Hz)

Voltage Drop at Surge Current Apply ±Dynamic Current Limit of Break Switches Forward Voltage - 5 - V

PARAMETERS RELATED TO PROTECTION SCR

Surge Current Twice ±Dynamic Current Limit of Break Switches - - 4 A Gate Trigger Current -V Hold Current 110 - mA Gate Trigger Voltage Trigger Current V Reverse Leakage Current V ON-state Voltage (Note 10) 0.5A, t = 0.5µs

NOTES:

10. In some instances, the typical ON-state voltage can range as low as -25V.

SUPPLY MIN TYP MAX UNITS

BAT

Apply ±DC Current Limit of Break Switches Forward Voltage - - 3 V

Current - 50 - mA

BAT

2.0A, t = 0.5µs

4.5 - 5.5 V

-19 - -72 V

TABLE 7. POWER SUPPLY SPECIFICATIONS

- 4V - V

BAT

--1.0µA

-3

-5

- 2V V

BAT

V V

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TABLE 8. PIN DESCRIPTIONS - ISL5571A

PIN NO.

2T 3T

NAME DESCRIPTION

GND

BAT

LINE

Fault Ground. Internally, this pin is electrically isolated from D

GND.

Connect to TIP on SLIC side. 15 R Connect to TIP on line or phone side. 14 R

PIN NO.

16 V

NAME DESCRIPTION

BAT

Battery Voltage. Used as a reference for protection circuit. Provides Trigger current for the protection SCR.

BAT

LINE

Connect to RING on SLIC side.

Connect to RING on line or phone side. 4 NC No Connection. 13 NC No Connection. 5 NC No Connection. 12 R 6T

RING

7V 8T

Connect to Return Ground for Ringing Generator. 11 LATCH Logic State Latch Control, active-high,

+5V supply. 10 INPUT Logic Level Input Switch Control.

Temperature Shutdown Pin. Can be used as a logic level

input or output. See Truth Table. As an output, will read

RING

GND

Connect to ringing generator.

transparent low.

Digital Ground. Internally, this pin is

electrically isolated from F

+5V when device is in its operational mode and 0V in the thermal shutdown mode. In the ISL5571A, the thermal shutdown mechanism cannot be disabled.

Pinout

ISL5571A

TOP VIEW

GND

TIP

RING

†

TLINE EXTERNAL PROTECTOR MAXIMUM VOLTAGE PRIOR TO SWITCHING TO THE ON STATE SHOULD NOT EXCEED 130V.

RLINE EXTERNAL PROTECTOR MAXIMUM

†

VOLTAGE PRIOR TO SWITCHING TO THE ON STATE SHOULD NOT EXCEED 220V.

EXTERNAL CROWBAR

PROTECTION

LINE

†

LINE

- 48 V

RING

RING RETURN

RING

SW3

TIP LINE BREAK

SW1

RING LINE BREAK

RING ACCESS SW4

12 11 10 8

GEN

RING GENERATOR

BATTERY

SW2

INPUTLATCH

BAT

SCR

CONTROL LOGIC

GND

TSD

BAT

GND

BAT

+ 5 V

TIP

SLIC

RING

GND

RRLY

FIGURE 1. APPLICATION CIRCUIT

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TABLE 9. TRUTH TABLE - ISL5571A

LOGIC INPUTS SWITCH CONDITION

RINGING

TIP LINE BREAK

LOGIC STATE

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) POWER RINGING

LATCHED (Note 12) 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.

LATCH INPUT T

1 0 1 or Floating (Note 11) ON ON OFF OFF

1 1 1 or Floating (Note 11) OFF OFF ON ON

SWITCH

RING LINE BREAK

SWITCH

RETURN

SWITCH

RING ACCESS

SWITCH

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 r break switches for optimal longitudinal balance, higher temperature operation (enabling continuous operation in

matching between the line

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 Logi c 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:

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Idle / Talk State (LATCH = 0, INPUT = 0, TSD = 1 or

Floating) In this state the Line Break switches (SW1 and SW2) are

closed (on) and the Ring Return and Ring Access switches (SW3 and SW4) are open (off). The subscriber line circuit is either on-hook or off-hook:

1. In the on-hook condition, the SLIC is monitoring the Tip and Ring lines through the Line Break switches for an offhook condition. This is called the Idle state.

2. In the off-hook condition, a telephone conversation between two or more parties is in progress or data is being transferred between modems. This is called the Talk state. The SLIC is providing DC power through the Line Break switches to the telephone handset for modulation. Modulated AC voice signals or data are traveling through the Line Break switches SW1 and SW2.

Power Ringing State (LATCH = 0, INPUT = 1, TSD = 1

or Floating) In this state the Line Break switches (SW1 and SW2) are

open (off) and the Ring Return and Ring Access switches (SW3 and SW4) are closed (on). For ring inj ec ted ring in g as shown in Figure 1, a ring generator is connected to the phone through the Ring Access switch (SW4) and returned to ground through the Ring Return switch (SW3).

All OFF State (LATCH = X, INPUT = X, TSD = 0)

In this state both the Line Access switches (SW1 and SW2) and the Ring Return and Ring Access switches (SW3 and SW4) are open (off). The ISL5571A will enter the All Off state when the following conditions occur:

1. The TSD pin is used as a control input and is programmed to logic low.

2. The device has enter thermal shutdown due to a fault condition. (Thermal Shutdown is described in the Auxiliary Functions and Features section below.)

3. If V

While in the All OFF state, communication and power ringing are inoperable because all the ISL5571A switches are open (off).

rises above -10V or disappears.

BAT

Logic State Latch (LATCH = 1, TSD = 1 or floating,

INPUT = 0 or 1) A Logic State Latch is Integrated into the ISL5571A, see

Figure 2. If the LATCH control pin is high and the TSD pin is high or floating, the device will no longer respond to logic level changes at the INPUT pin. The state of the switches will be determined by the logic level of the INPUT pin at the time the LATCH pin transitions from logic low to logic high. The state of the switches at the time of this transition will be permanently held as long as the LATCH pin is high. When

the LATCH pin is taken low the device will again be under the control of the INPUT pin and the switches will immediately go to the state specified by the logic level at the INPUT pin. (Note: The TSD pin overrides the LATCH pin and the INPUT pin. When the TSD pin is low the ISL5571A goes to the ALL OFF state regardless of the logic levels applied at the LATCH pin and the INPUT pin.)

ISL5571A

LOGIC

SWITCHES

FIGURE 2. BLOCK DIAGRAM OF LOGIC CONTROL

CONTROL

CIRCUITRY

LOGIC STATE LATCH

LATCH

INPUT10

TSD8

INPUT Pin

The INPUT pin (pin 10) is the main logic input control pin. Reference Table 9 for logic state table. When the LATCH pin is low and the TSD pin is high or floating, you can toggle back and forth between the Idle / Talk state and the Power Ringing state by changing the logic level at the INPUT pin. This is the normal operating mode of the device.

NOTE: If the LATCH pin is high, the INPUT pin is no

longer active and the device will no longer respond to logic changes at the INPUT pin.

The TSD pin overrides all other logic pins. If the TSD pin is low, the device will enter an All OFF state and will no longer respond to logic changes at the INPUT pin.

Latch Pin

The LATCH pin (pin 11) is the control for the Logic State Latch. Reference Table 9 for logic state table. When the LATCH pin is low, the latch is disabled and the state of the ISL5571A will be determined by the logic level applied at the other logic inputs.

When the LATCH pin is high, the latch is active and the logic state of the switches at the time the LATCH pin went high will be latched. As long as the LATCH pin is held high the switches will not respond to logic changes at the INPUT control pin.

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TSD Pin

The TSD pin (pin 8) can be used as a logic level input or output. Reference Table 9 for logic state table. The TSD pin overrides all other logic pins.

As an input, if this pin is driven low, either by external logic applied to it or by the internal thermal shutdown circuitry, the ISL5571A device will enter the All OFF state. In the All OFF state all switches of the ISL5571A are open (off).

As an output, it is capable of driving a TTL input (2.8V at 200µA). The TSD pin will read +5V when the device is in normal operating mode and 0V when the device is in thermal shutdown. This pin can be monitored on an oscilloscope to determine if the ISL5571A device has enter thermal shutdown. (Thermal Shutdown is described in the Auxiliary Functions and Features section below.)

Connecting the TSD pin to 5V will have no effect on the performance of the ISL5571A device and will not disable the thermal shutdown circuitry.

Auxiliary Functions and Features

In addition to the ISL5571A main function of momentarily connecting and disconnecting an external ring generator to ring the phone, the ISL5571A device also provides surge and power-cross protection to the SLIC and CODEC. This fault protection is provided by a combination of currentlimiting circuitry, a thermal shutdown mechanism and an over-voltage clamping circuit. Another feature the device offers is a V describes each in detail.

Current Limiting

The Line Break switches (SW1 and SW2) and the Ring Return switch (SW3) are all current-limited. These switches have a DC current limiting response and a dynamic current limiting response which were built into the device to provide protection during lightning and power-cross faults. Each of these current limiting responses are explained below.

DC CURRENT LIMITING RESPONSE

The ON state V-I Graph for SW1, SW2, and SW3 is shown in Figure 3. It represents the DC current limiting response of the switches. The graph shows that over a certain range of positive and negative voltages, the current and voltage relationship is linear and behaves according to Ohms law (V = IR). Note: At around ±1.5V an inflection point occurs decreasing the on resistance by 2/3. The on resistance specified in the data sheet is measured in the region prior to the inflection point (between ±1.5V).

When current through the switch reaches the current limit of the switch, the current is clamped and held at a constant value. The switch then operates as a constant current source. Increasing the voltage beyond this point will not change the value of the current.

fault detection circuit. The following

BAT

LIMIT

-1.5

LIMIT

-I

+1.5

T2 > T1

-V

2/3 r

FIGURE 3. ON STATE V-I GRAPH OF SW1, SW2 AND SW3

FIGURE 4. EFFECT OF TEMPERATURE ON DC CURRENT

CURRENT LIMITING

-V

LIMIT

CURRENT LIMITING

2/3 r

0.5µs

FIGURE 5. DYNAMIC CURRENT LIMIT RESPONSE

TIME

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The DC current limiting response has a negative temperature coefficient. As the temperature of the device increases the DC current limit of the switch will decrease. This is illustrated in Figure 4.

Figure 4 shows the V-I curves of a sw itch at t wo di fferen t die temperatures, T1 and T2. In this illustration T2 is greater in temperature than T1. This shows that when a switch is driven into current limit and held there, the current limit will decrease over time as the switch temperature increases. If the power through the switch is great enough, the temperature of the switch will continue to increase until the switch goes into thermal shutdown (Thermal Shutdown is described below).

Dynamic Current Limiting Response

The DC current limit response described above pertains to DC and AC voltage sources applied across the switches. The dynamic response is the response of the current limit circuit to a fast or high dv/dt pulse. The dynamic response would be seen, for example, during a lightning surge

Figure 5 shows the dynamic response that is observed when SW1, SW2 or SW3 is surged with a 1000V at 10/1000µs telecom surge pulse. (Note: This surge test is done with the switch in the on state and with the appropriate external secondary protection in place.) The dynamic current limit of SW1, SW2 or SW3 will limit the current through the switch to less than 2.0A for 0.5µs as shown in Figure 5. Once the switch has turned off, the voltage at the T terminals will increase to a point where the external secondary protection device will trigger and crowbar the voltage at T ISL5571A against damage.

Since the Line Break switches (SW1, SW2) have this dynamic current limit feature, the internal over-voltage protection clamping circuit of the ISL5571A device will need to only protect the SLIC against a 2.0A ≤0.5µs pulse during a lightning surge.

Line

and R

to a low voltage, protecting the

Line

and R

Line

Thermal Shutdown (TSD)

The ISL5571A has a built in thermal shutdown protection circuit. The thermal shutdown protection mechanism is invoked if a fault condition causes the junction temperature of the die to exceed about 150°C exceeded the thermal shutdown circuitry will force the switches into an All OFF state, regardless of the logic inputs. While in thermal shutdown the TSD logic pin (pin 11) will be driven low by the thermal shutdown circuit. (Note: During normal operation the TSD pin is high.) The thermal shutdown mechanism was designed to have a thermal hysteresis of about 12°C. device will begin to cool down, because all the switches are off and no current flows. When the temperature of the die cools to about 138°C shutdown and the switches will close again. If the fault

Once in thermal shutdown the

the ISL5571A will cycle out of thermal

. Once the thermal limit is

condition is still present, the temperature of the die will again increase and this cycle will be repeated.

Over Voltage Protection Clamping Circuit

The ISL5571A contains an over-voltage clamping circuit on the SLIC side of the Line Break switches, see Figure 1. This clamping circuit consists of a diode bridge and SCR. During lightning surges and power-cross fault conditions this circuit will clamp the voltage at the T SLIC to a safe level and will shunt harmful currents to ground away from the SLIC.

The clamping circuit is externally connected to ground through the F voltage of the SLIC is connected to the clamping circuit through the V diode bridge and the SCR circuit is described below.

DIODE BRIDGE WITH SCR (ISL5571A)

During a positive lightning surge or during the positive cycle of a power-cross / induction fault, the voltage at the T and R drop above ground. The fault current will flow harmlessly through diodes D1 and D2 of the diode bridge to ground (see Figure 1).

During a negative lightning surge or during the negative cycle of a power-cross / induction fault when the voltage at the T than the V turn on. When the SCR turns on and latches, it will crowbar the voltage at the T state, approximately 3 diode drops below ground. This lowvoltage on state will cause the current resulting from the over voltage to be safely direct to ground through diodes D3 and D4 of the diode bridge and the SCR (see Figure 1). Once the fault current decrease below the protection SCR holding current (110mA) the SCR will turn off and the SLIC will be able to return to normal operation.

BAT

terminals of the SLIC will be clamped to a diode

BAT

and R

BAT

Fault Circuit Protection - Loss of Battery

pin (pin 1) of the device. The battery

GND

pin (pin 16) of the device. The operation of

BAT

terminals reach 2V to 4V more negative

BAT

voltage, the protection SCR will trigger and

and R

BAT

and R

BAT

lines to a low-voltage

BAT

terminals of the

BAT

Voltage

The ISL5571A device contains a V monitors the SLIC battery voltage (V detects that the V cause the ISL5571A to enter the All OFF state. All the switches will remain off (open) until the circuit detects that the SLIC battery voltage has dropped below -15V.

voltage has risen above -10V, it will

BAT

fault circuit which

BAT

). When this circuit

BAT

Design Considerations

External Protection

Subscriber line card circuits using the ISL5571A require the use of an external protection circuit on the loop side or phone side of the device, see Figure 1. This protection is required to minimize the power stress on the ISL5571A during overvoltage and overcurrent conditions. When the proper external protection circuitry is used in conjunction

ISL5571A

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with the integrated secondary protection, features offered by the ISL5571A, the application circuit will pass the AC powercross and lightning immunity tests of the following regulatory requirements:

• GR 1089-CORE

•ITU-T K.20 This section will discuss the issues that must be considered

when designing an external protection circuit for use with the ISL5571A.

The external protection circuitry should be designed to limit the peak voltages on the T ISL5571A. The most potentially stressful condition concerning the ISL5571A is low level power-cross when the ISL5571A switches are closed. Under this condition, the external protection circuitry limits the voltage and corresponding power dissipation until the ISL5571A thermal shutdown circuitry opens the switches.

The external protector chosen for the T must limit at a maximum of 130V thereby limiting the power stress on the Ring Return switch (SW3).

The protector chosen for the R maximum of 220V thereby limiting the power stress on the Line Break switch (SW2). The 220V break-over voltage of the protector on RLine is large enough to not interfere with the AC ring signal during ringing.

Texas Instruments and Teccor Electronics have designed specific parts to protect solid state line card access switches. The following protectors are recommended:

Texas Instruments Part Number TISPL758LF3D(T and R

Teccor Electronics Part Number P1200SC (T

P2000SC (R

Refer to the above company’s data sheets for information on their parts and reference designs for protection of solid state line card access switches, see Related Literature section on Page One.

Line

)

Line

and R

Line

)

terminals of the

Line

terminal

Line

terminal must limit at a

) and

Line

Break-Before-Make Operation

The ISL5571A device inherently has a Break-before-Make condition between the following switches:

a. Between the Line Break switch SW1 and the Ring

Return switch SW3 during the transition from the Idle state to the Power Ringing state.

b. Between the Line Break switch SW2 and the Ring

Access switch SW4 during the transition from the Idle state to the Power Ringing state.

Make-Before-Break Operation

The ISL5571A device could exhibit a Make-before-Break condition between the Line Break switch SW2 and the Ring Access switch SW4 during the transition from the Power

Ringing state to the Idle / Talk state. There is a period of time that can be as much as 25ms (1/2 cycle of the 20Hz ring signal) when both SW2 and SW4 will both be on (closed). This occurs because SW4 is an SCR and requires a zero current crossing to turn off.

Protection SRC Latch-Up

In the Make-before-Break condition, when transiting from the Power Ringing state to the Idle/ Talk state, during the negative cycle of the ring generator it is possible for enough current to flow that the protection SCR will turn on. This will result in shorting the ring generator and the Ring terminal of the SLIC to ground. When either SW2 or SW4 turns off, the Ring terminal of the SLIC will remain shorted to ground unless the output current limit of the SLIC is less than the holding current (110mA) of the protection SCR. The current limit of most SLICs are set well below the 110mA minimum holding current of the ISL5571A protection SCR and therefore should not be a concern. Another method to prevent latch-up of the protection SCR would be to strobe the TSD pin of the ISL5571A. as discussed in Break-Before-Make section.

Ring Access Switch Quiescent Current During Ringing

The Ring Access switch (SW4) is a silicon control rectifier type switch (SCR). During power ringing, the Ring Access switch will draw a nominal 2mA of current from the ring generator. This current is called I equal to:

RING QUIESCENT

System designers need to ensure that this additional current can be provided by the ring generator.

= I

RING GEN

RING QUIESCENT

- I

RING LOAD

and is

Glossary of Acronyms

AC = Alternating Current BIMOS = Bipolar Metal-Oxide Semiconductor CO = Central Office CODEC = CODer-DECoder DC = Direct Current DLC = Digital Loop Carrier DAML = Digitally Added Main Line EMI = Electromagnetic Interference ESD = Electrostatic Discharge FITL = Fiber in the Loop HFC = Hybrid Fiber Coax ICs = Integrated Circuits LCAS = Line Card Access Switch PBX = Private Branch Exchange REN = Ring Equivalency Number MOSFET = Metal-Oxide Semiconductor Field-Effect Transistor SCR = Silicon Control Rectifier SLIC = Subscriber Line Interface Circuit SMDs = Surface Mount Devices SOIC = Small Outline Integrated Circuit TSD = Thermal ShutDown TTL = Transistor-Transistor Logic

Small Outline Plastic Packages (SOIC)

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ISL5571A

INDEX AREA

123

-AD

0.25(0.010) C AM BS

NOTES:

1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of Publication Number 95.

2. Dimensioning and tolerancing per ANSI Y14.5M-1982.

3. Dimension “D” does not include mold flash, protrusions or gate burrs. Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side.

4. Dimension “E” does not include interlead flash or protrusions. Interlead flash and protrusions shall not exceed 0.25mm (0.010 inch) per side.

5. The chamfer on the body is optional. If it is not present, a visual index feature must be located within the crosshatched area.

6. “L” is the length of terminal for soldering to a substrate.

7. “N” is the number of terminal positions.

8. Terminal numbers are shown for reference only.

9. The lead width “B”, as measured 0.36mm (0.014 inch) or greater above the seating plane, shall not exceed a maximum value of 0.61mm (0.024 inch)

10. Controlling dimension: MILLIMETER. Converted inch dimensions are not necessarily exact.

-B-

SEATING PLANE

-C-

0.25(0.010) BM M

0.10(0.004)

h x 45

M16.3 (JEDEC MS-013-AA ISSUE C)

16 LEAD WIDE BODY SMALL OUTLINE PLASTIC PACKAGE

INCHES MILLIMETERS

SYMBOL

A 0.0926 0.1043 2.35 2.65 -

A1 0.0040 0.0118 0.10 0.30 -

B 0.013 0.0200 0.33 0.51 9 C 0.0091 0.0125 0.23 0.32 D 0.3977 0.4133 10.10 10.50 3 E 0.2914 0.2992 7.40 7.60 4

e 0.050 BSC 1.27 BSC -

H 0.394 0.419 10.00 10.65 -

h 0.010 0.029 0.25 0.75 5 L 0.016 0.050 0.40 1.27 6

N16 167

Rev. 0 12/93

NOTESMIN MAX MIN MAX

All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems.

Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality

Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is ca utioned to verify that data she ets are current before pl acing orders. Information fur nished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or othe rwise under any patent or patent rights of Intersil or its subsidia ries.

For information regarding Intersil Corporation and its products, see www.intersil.com

intersil ISL5571A DATA SHEET

Specifications and Main Features

Frequently Asked Questions

User Manual