ISL6401EVAL1

ISL6401EVAL1 Datasheet

Using the ISL6401 RSLIC PWM Controller

Part	Datasheet
ISL6401EVAL1	ISL6401EVAL1 (pdf)

Related Parts	Information
ISL6401EVAL1Z	ISL6401EVAL1Z

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Using the ISL6401 RSLIC PWM Controller Evaluation Board Application Note January 30, 2009 AN1082.2 Author Manisha Pandya, Jason Houston Functional Description The ISL6401 pulse width modulating PWM current mode controller is designed for a wide range of DC/DC conversion applications including boost, flyback, and isolated output configurations. The device is optimized to provide high performance, low-cost solution for Ringing SLIC RSLIC Ring Vbh and Talk Vbl power supplies in VoIP applications. The IC features an integrated inverter that is ideal for generating negative output voltage like RSLIC Ring Vbh -72V and Talk Vbl -24V , -48V for IP Phones, -5V and -15V for DSL CO line drivers. The output voltages are adjusted with an external voltage divider. Peak current mode control architecture effectively handles Ring trip transients and provides inherent overcurrent protection. Flyback topology allows the operation close to 50% duty cycle, offering optimum transformer utilization, low ripple current and less stress on input/output capacitors. Internal soft-start minimizes start-up stress without any external components. The switching frequency can be programmed from 50kHz to 600kHz or alternatively, the internal oscillator can be locked to an external clock fed at SYNC input for noise sensitive applications. A logic level shutdown input is included, which reduces supply current to 55µA in the shutdown mode. DC/DC conversion efficiency is optimized by use of a low current sense voltage. For a detailed functional description, complete specifications and component selection guidelines, please refer to the ISL6401 Data Sheet “ISL6401 Synchronizing Current Mode PWM for Subscriber Line Interface Circuits” , Intersil Corporation, FN9007, available on Intersil’s website, Application Information As worldwide demand for inexpensive Voice over Internet Protocol telephony grows, so will the need for Integrated Circuits that are specialized to enable compatibility between new telephony systems and older telephones based on analog standards. Analog ring signal generation and off hook loop current supply are two analog functions that are performed by Subscriber Line Interface Circuits SLICs . This application note discusses the special power supply implementation to generate the high negative voltages needed by SLICs. Overview of Telephone Loop System Traditionally, a telephone network consists of a circuit between the subscriber and the central office. However, the advent of new high speed digital technologies has created the need to control and manage the functions of the phone locally as opposed to the central office. In both instances the principals governing the operation of the phone loop are essentially the same. In a telephone loop, the subscriber is connected to the network via 2 wires, commonly known as Tip and Ring. The actual digital telecommunications trunk line however, operates on 4 wires two of which are allocated for transmitting and two for receiving. This 2 to 4-wire interface consists of the SLIC and CODEC. A SLIC is the primary interface between the 4-wire ground referenced low voltage switch environment and the 2-wire floating high voltage loop environment. It performs a number of important functions including Battery feed, Overvoltage protection, Ringing, Signaling, Coding, Hybrid Balancing and also Testing. The Ringing SLIC RSLIC typically requires two high voltage power supply inputs. The first is a tightly regulated voltage around -24V or -48V for off-hook signal transmission. The second is a loosely regulated -70V to -100V for ring tone generation. When the switch hook is released the phone puts approximately 200Ω of resistance across the phone terminals. Intersil RSLICs feature internal current limiting so this load is not presented to the power supply. However, not all of the SLICs available in the market offer this feature and the power supply is expected to maintain output during the remainder of the ring cycle. Once voice transmission begins, the SLIC, in many cases, requires a lower voltage input to establish a 20mA to 25mA current loop. The loop feeds the 200Ω, protection resistors, and line resistances within the phone. In some cases, the lower supply and higher supply voltage are combined and the SLIC runs from a compromise voltage of approximately -53V. The specifications listed in the following table are for a 4-line requirement with 5 REN per line. TABLE TYPICAL POWER SUPPLY REQUIREMENT FOR VoIP RESIDENTIAL GATEWAY PARAMETER REQUIREMENT Input Voltage 5V or 12V Output Power 3W to 10W Efficiency 80% to 90% Output Voltages -24V, -72 to -100V and/or -48V -24V Requirements 4 lines -72V Requirements 4 lines Regulation ±5% Maximum Output Current 0.10A Ripple Less than 0.25VP-P Regulation ±10% Maximum Output Current 0.10A Ripple Less than 1VP-P CAUTION These devices are sensitive to electrostatic discharge follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 \| Intersil and design is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2003, 2005, All Rights Reserved All other trademarks mentioned are the property of their respective owners. Application Note 1082 Using the ISL6401EVAL1Z Evaluation Board The ISL6401EVAL1Z Schematic shows a current mode power supply using the Intersil ISL6401 in standard flyback topology. The ISL6401EVAL1Z evaluation board is shipped “ready to use” right from the box. The IC requires +5V Bias. The evaluation board input voltage can be 10V to 16V with the specified transformer and external components. The output voltages are -24V at 120mA and -72V at 120mA. The board is capable of evaluating device operation with loads that simulate one, two, three or four line operation. The use of an electronic load enables evaluation over a wide range of operating conditions. Simply vary the load on each output from 0mA to 120mA in any combination to match exact application requirements. The circuit uses off-the-shelf inexpensive transformers to generate both outputs using a single controller. The transformer turns ration is 1:1:1:1 where 24V appear across each secondary winding and the primary during the switch off-time. The remaining secondary windings are stacked in series to develop -48V. The -48V section is then stacked on the -24V section to get the -72V. This technique provides good cross regulation, lowers the voltage rating required for the output capacitors and lowers the RMS current, allowing the use of cheaper output capacitors. Also, the selection of a transformer with multifilar winding lowers the leakage inductance and cost. The cross regulation of both output is achieved by using split feedback for both outputs where the feedback factor can be weighed based on load condition on both outputs. TABLE ISL6401EVAL1Z EVALUATION BOARD

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Using the ISL6401 RSLIC PWM Controller

Evaluation Board

Application Note

January 30, 2009

AN1082.2

Author Manisha Pandya, Jason Houston

Functional Description

The ISL6401 pulse width modulating PWM current mode controller is designed for a wide range of DC/DC conversion applications including boost, flyback, and isolated output configurations. The device is optimized to provide high performance, low-cost solution for Ringing SLIC RSLIC Ring Vbh and Talk Vbl power supplies in VoIP applications. The IC features an integrated inverter that is ideal for generating negative output voltage like RSLIC Ring Vbh -72V and Talk Vbl -24V , -48V for IP Phones, -5V and -15V for DSL CO line drivers. The output voltages are adjusted with an external voltage divider.

Peak current mode control architecture effectively handles Ring trip transients and provides inherent overcurrent protection. Flyback topology allows the operation close to 50% duty cycle, offering optimum transformer utilization, low ripple current and less stress on input/output capacitors. Internal soft-start minimizes start-up stress without any external components. The switching frequency can be programmed from 50kHz to 600kHz or alternatively, the internal oscillator can be locked to an external clock fed at SYNC input for noise sensitive applications. A logic level shutdown input is included, which reduces supply current to 55µA in the shutdown mode. DC/DC conversion efficiency is optimized by use of a low current sense voltage.

For a detailed functional description, complete specifications and component selection guidelines, please refer to the ISL6401 Data Sheet “ISL6401 Synchronizing Current Mode PWM for Subscriber Line Interface Circuits” , Intersil Corporation, FN9007, available on Intersil’s website,

Application Information

As worldwide demand for inexpensive Voice over Internet Protocol telephony grows, so will the need for Integrated Circuits that are specialized to enable compatibility between new telephony systems and older telephones based on analog standards. Analog ring signal generation and off hook loop current supply are two analog functions that are performed by Subscriber Line Interface Circuits SLICs . This application note discusses the special power supply implementation to generate the high negative voltages needed by SLICs.

Overview of Telephone Loop System

Traditionally, a telephone network consists of a circuit between the subscriber and the central office. However, the advent of new high speed digital technologies has created the need to control and manage the functions of the phone locally as opposed to the central office. In both instances the
principals governing the operation of the phone loop are essentially the same.

In a telephone loop, the subscriber is connected to the network via 2 wires, commonly known as Tip and Ring. The actual digital telecommunications trunk line however, operates on 4 wires two of which are allocated for transmitting and two for receiving. This 2 to 4-wire interface consists of the SLIC and CODEC. A SLIC is the primary interface between the 4-wire ground referenced low voltage switch environment and the 2-wire floating high voltage loop environment. It performs a number of important functions including Battery feed, Overvoltage protection, Ringing, Signaling, Coding, Hybrid Balancing and also Testing.

The Ringing SLIC RSLIC typically requires two high voltage power supply inputs. The first is a tightly regulated voltage around -24V or -48V for off-hook signal transmission. The second is a loosely regulated -70V to -100V for ring tone generation. When the switch hook is released the phone puts approximately 200Ω of resistance across the phone terminals. Intersil RSLICs feature internal current limiting so this load is not presented to the power supply. However, not all of the SLICs available in the market offer this feature and the power supply is expected to maintain output during the remainder of the ring cycle. Once voice transmission begins, the SLIC, in many cases, requires a lower voltage input to establish a 20mA to 25mA current loop. The loop feeds the 200Ω, protection resistors, and line resistances within the phone. In some cases, the lower supply and higher supply voltage are combined and the SLIC runs from a compromise voltage of approximately -53V.

The specifications listed in the following table are for a 4-line
requirement with 5 REN per line.

TABLE TYPICAL POWER SUPPLY REQUIREMENT FOR VoIP RESIDENTIAL GATEWAY

PARAMETER

REQUIREMENT

Input Voltage
5V or 12V

Output Power
3W to 10W

Efficiency
80% to 90%

Output Voltages
-24V, -72 to -100V and/or -48V
-24V Requirements 4 lines -72V Requirements 4 lines

Regulation ±5% Maximum Output Current 0.10A Ripple Less than 0.25VP-P

Regulation ±10% Maximum Output Current 0.10A Ripple Less than 1VP-P

CAUTION These devices are sensitive to electrostatic discharge follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil and design is a registered trademark of Intersil Americas Inc.

Copyright Intersil Americas Inc. 2003, 2005, All Rights Reserved

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

Application Note 1082

Using the ISL6401EVAL1Z Evaluation Board

The ISL6401EVAL1Z Schematic shows a current mode power supply using the Intersil ISL6401 in standard flyback topology. The ISL6401EVAL1Z evaluation board is shipped “ready to use” right from the box. The IC requires +5V Bias. The evaluation board input voltage can be 10V to 16V with the specified transformer and external components. The output voltages are -24V at 120mA and -72V at 120mA. The board is capable of evaluating device operation with loads that simulate one, two, three or four line operation. The use of an electronic load enables evaluation over a wide range of operating conditions. Simply vary the load on each output from 0mA to 120mA in any combination to match exact application requirements. The circuit uses off-the-shelf inexpensive transformers to generate both outputs using a single controller. The transformer turns ration is 1:1:1:1 where 24V appear across each secondary winding and the primary during the switch off-time. The remaining secondary windings are stacked in series to develop -48V. The -48V section is then stacked on the -24V section to get the -72V. This technique provides good cross regulation, lowers the voltage rating required for the output capacitors and lowers the RMS current, allowing the use of cheaper output capacitors. Also, the selection of a transformer with multifilar winding lowers the leakage inductance and cost. The cross regulation of both output is achieved by using split feedback for both outputs where the feedback factor can be weighed based on load condition on both outputs.

TABLE ISL6401EVAL1Z EVALUATION BOARD

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Datasheet ID: ISL6401EVAL1 639191