Operation of the HC5503EVAL Evaluation Board TM Application Note July 1997 AN9736.1 Features HC5503 Board SLIC Controls • Includes the Ringing Relay The design of the HC5503 board incorporates three SPDT center off switches. The three SPDT switches (RS, RC, PD) control the functional state of the SLIC. If off-board mode control of the SLIC is desired, the three SPDT switches can be set to center open position and driven by logic at the logic terminal port. The logic terminal port is located in the upper left hand corner of the board. • Toggle Switch Programming for Logic States • Monitoring of Switch Hook Detect (SHD) via On Board LED’s • Includes On-Board Op Amp for Evaluation of Transhybrid Balance • Logic Terminal Port for Easy Evaluation in Existing Systems Functional Description Mode Control Switches Toggling RS, RC or PD towards the top of the board (Intersil logo to bottom left) results in a logic “1” state on the pin; and toggling them towards the bottom results in a logic “0” state on the pin. The HC5503 Subscriber Line Interface Circuit (SLIC) evaluation board has provisions for: Full evaluation of the voice and DC feeding characteristics, ring injected single ended ringing, and transhybrid balance. Functional control of the SLIC is provided using the toggle switches RS, RC and PD. See Table 7 for the logic states. Getting Started The HC5503 evaluation board is configured to match a 600Ω line impedance. Resistors RB1 and RB2 account for 300Ω and the remaining 300Ω is synthesized via feedback through resistor R2. Reference the HC5503 data sheet for more details about impedance matching. Verify that the sample HC5503 included with the evaluation board is oriented in its socket correctly. Correct orientation is with pin 1 pointing towards the onboard pin 1 designator located to the left of the socket (reference the data sheet for location of device pin 1). Power Requirements for the HC5503 Verifying the HC5503 Operation Power Supply Connections The operation of the HC5503 and the sample part can be verified by performing six tests: The HC5503 requires three external power supplies for a complete evaluation of the application. The SLIC is powered by two supplies VBAT = -24V and VCC = +5V and the third supply (VEE = -5V) powers an external op-amp (U2) for the transhybrid balance circuit. This op-amp is usually contained in the CODEC. A common ground must exist between the HC5503 evaluation board and the off board logic. A differential ground voltage may result in erroneous logic states at the SLIC inputs. 1. Power Supply Current Verification. 2. Normal Loop Feed Mode Verification. 3. Tip and Ring Voltage Verification. 4. Gain Verification (4-wire to 2-wire). Ground Connections 5. Ring Trip Detector Verification. The HC5503 board has tied the analog, digital and battery grounds to a common ground plane designated GND. It is recommended that the analog, digital and battery grounds of the SLIC be tied together as close to the device pins as possible. The three external power supplies should each be grounded to the evaluation board. 6. Transhybrid Balance Verification. 1 The above 6 tests require the following equipment: a 600Ω load, an AC volt meter, three external supplies (one each for VCC, VEE, and VBAT), an oscilloscope, a telephone and a battery backed AC source. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a trademark of Intersil Americas Inc. Copyright © Intersil Americas Inc. 2002. All Rights Reserved Application Note 9736 Application Tip: When terminating tip and ring, it is handy to assemble terminators using a Pomona MDP dual banana plug connector as the terminating resistor receptacle. Refer to Figure 1 for details. Setup: 1. Set the mode switches for “Power Denial” mode: RS = 1, RC = 0/1, PD = 0. GND 2. Terminate HC5503 SLIC with a 600Ω load. A B 3. Measure the supply currents and compare to those in Table 1. TABLE 1. 600Ω SUPPLY FIGURE 1. TERMINATION ADAPTER Using the termination shown in Figure 1 provides an unobtrusive technique for terminating tip and ring while still providing access to both signals using the banana jack feature of the MDP connector. Posts are also available that fit into holes A and B, providing a solderable connection for the terminating resistor. RL (Ω ) MODE HC5503 TYP (mA) VCC = +5V 600 Normal Loop Feed 7.2 VEE = -5V 600 Normal Loop Feed 0.74 VBAT = -24V 600 Normal Loop Feed 20.7 VBAT = -24V 600 Power Denial 1.0 Test # 1 Power Supply Current Verification Test # 2 Normal Loop Feed Mode Verification A quick check of evaluation board and the HC5503 sample is to measure the supply currents. The readings should be similar to the values listed in Table 1. The measurements can be made using a series ammeter on each supply, or power supplies with current displays. This test verifies loop current operation and loop current detection in the Normal Loop feed mode via the on-board LED. Normal Loop Feed Discussion: The currents measured include those of the SLIC and supporting circuitry. For SLIC supply currents consult the HC5503 data sheet. Discussion: When power is applied to the SLIC a loop current will flow from tip to ring through the 600Ω load. Loop current detection occurs when this loop current triggers an internal detector that pulls the output of SHD low, illuminating the LED through the +5V supply. Once the LED illuminates, remove the 600Ω termination and verify that the LED turns off. Setup: 1. Connect the power supplies to the HC5503. Setup: 1. Connect the power supplies to the HC5503. 2. Set VBAT to -24V. 2. Set the mode switches for “Normal Loop Feed” mode: RS = 1, RC = 1, PD = 1. 3. Terminate the HC5503 with 600Ω load across Tip and Ring. 3. Terminate HC5503 SLIC with a 600Ω load. 4. Set the mode switches for “Normal Loop Feed” mode: RS = 1, RC = 1, PD = 1. 4. Measure the supply currents and compare to those in Table 1. Verification: 1. The SHD LED is on when tip and ring are terminated with 600Ω. Power Denial Discussion: 2. The SHD LED is off when tip and ring are open circuit. Power denial limits power to the subscriber loop: it does not power down the SLIC, i.e., the SLIC will still consume its normal on-hook quiescent power during a power denial period. This function is intended to “isolate” from the battery, under processor control, selected subscriber loops during an overload or similar fault status. If power denial is selected, the logic circuitry switches in a current source to charge up the external capacitor C3. As C3 charges up, the ring voltage approaches the tip voltage. Since tip is always biased at -4V, the battery feed across the loop is essentially zero, and minimum loop power will be dissipated if the circuit goes off-hook. No signalling functions are available during this mode. 2 Test # 3 Tip and Ring Voltage Verification This test verifies the tip and ring voltages for both the Normal Feed and Power Denial Modes. Setup: 1. Connect the power supplies to the HC5503. 2. Set VBAT to -24V. 3. Disconnect the 600Ω load across Tip and Ring. 4. Set the mode switches for “Normal Loop Feed” mode: RS = 1, RC = 1, PD = 1. Application Note 9736 5. Measure tip and ring voltages with respect to ground and compare to those in Table 2. 6. Repeat the above test with the SLIC in the Power Denial Mode: RS = 1, RC = 0/1, PD = 0 and compare to those in Table 2. Setup: 1. Connect the power supplies to the HC5503. 2. Set the mode switches for “RD active (Ringing)” mode: RS = 1, RC = 0, PD = 1. 3. Connect the telephone across tip and ring. TABLE 2. MODE PART TIP TYP (V) RING TYP (V) 4. Connect battery backed AC (20Hz oscillator) to GENHI (VBAT + 90VRMS) banana jack. Verification: Normal Loop Feed (VBAT = -24V) -3.2 -21.0 Power Denial (VBAT = -24V) -3.2 -3.0 2. While ringing and on-hook, SHD LED is not illuminated. 3. While ringing, going off-hook will illuminate the SHD LED. Test #4 Gain Verification (4-Wire to 2-Wire) This test will verify that HC5503 SLIC is operating properly and that the 4-wire to 2-wire gain is about 0.615 or -4.0dB. Discussion: When terminated with 600Ω load, the SLIC will exhibit about a -4.0dB gain from the VRX input pin to across tip and ring (VTR). When an open circuit exists, a mismatch occurs and the gain of the SLIC goes to about 0.869 or +2.0dB. Reference the HC5503 data sheet for more information concerning the feedback network for impedance matching. The dB gain is calculated in Equation 1. V TR dB = 20 × log ----------V RX 1. Phone starts ringing when power applied to test setup. (EQ. 1) CAUTION: Short time durations of off-hook should be maintained to protect the feed resistors. In systems, the ring relay is software controlled to turn off milliseconds after off-hook is detected, hence limiting power dissipated in the feed resistors. 4. When phone is returned to on-hook, SHD LED will turn off. 5. Configure SLIC in Normal Loop Feed mode to stop phone from ringing. Set mode switches to RS = 1, RC = 1, PD = 1. Test #6 Transhybrid Balance Verification This test will verify the transhybrid balance circuitry. A low distortion AC signal source and a volt meter are the only additional hardware required to complete this test. Discussion: Setup: 1. Connect the power supplies to the HC5503. 2. Set the mode switches for “Normal Loop Feed” mode: RS = 1, RC = 1, PD = 1. Transhybrid balance is a measure of how well the input signal is canceled (that being received by the SLIC) from the transmit signal (that being transmitted from the SLIC). Without this function, voice communication would be difficult because of the echo. 3. Terminate HC5503 SLIC with a 600Ω load. Setup: 4. Connect a sine wave generator to the VRX input. 5. Set the generator for 1VRMS and 1kHz. 6. Connect an AC voltmeter across tip and ring. Verification: 1. Connect the power supplies to the HC5503. 2. Set the mode switches for “Normal Loop Feed” mode: RS = 1, RC = 1, PD = 1. 3. Terminate HC5503 SLIC with a 600Ω load. 1. Tip to ring AC voltage of 0.64VRMS when terminated. 2. Tip to ring AC voltage of 1.27VRMS when not terminated. 4. Set the AC source to 1VRMS, 1kHz and apply to the VRX input. 5. Connect an AC voltmeter between the VO and GND. Test #5 Ring Trip Detector Verification This test will verify the ringing function of the SLIC. A telephone and an AC signal source are the only additional hardware required to complete the test. Discussion: The 600Ω termination is not necessary for this test since the phone provides this nominal impedance when off-hook. Setting the mode switches as shown below will cause the relay driver pin (RD) of the SLIC to energize the relay that is on the evaluation board. 3 Verification: 1. Measure the AC voltage at VO output. 2. Calculate the Transhybrid balance using Equation 2 VO Transhybrid = 20 × log -------------------1V RMS 3. The value should be around -37.8dB. (EQ. 2) Application Note 9736 Functional Circuit COMPONENT Descriptions A brief description of each component is provided below. The components will be grouped by function to provide further insight into the operation of the HC5503 board. TABLE 6. AC DECOUPLING CAPACITORS C3, C4 AC decoupling capacitors TABLE 7. LOGIC CURRENT LIMITING RESISTORS TABLE 3. TWO WIRE SIDE, TIP AND RING RB1, RB2 Feed resistors that limit the current into the tip and ring inputs and are used for loop current detection. K1 Relay used to switch between normal loop feed operation and battery backed ring injected ringing. RD Relay Driver output. The RD pin is an open collector output that is used to control the ring relay (K1). RS1, CS1, RS2, CS2 RC snubber network placed across the ring relay contacts to minimize inductive kickback effects from the telephone ringer. D1, D2, D3, D4, MOV1, MOV2 Secondary surge protection. PTC R3, R4 TABLE 8. SUPPLY DECOUPLING CAPACITORS C5, C6, C8-11 Supply decoupling capacitors. TABLE 9. FEEDBACK RESISTORS R1, R2 Feedback resistors for synthesizing the AC 2-wire impedance. TABLE 10. SHD LED R5, D6 Provisions for a positive temperature coefficient (PTC) resistor. The PTC provides short circuit protection during ringing. The value of the PTC is application specific and therefore not provided with the board. R3 is the logic low current limiting resistor. R4 is the logic high current limiting resistor. R5 is the Current limiting resistors for the SHD, LED (D6). TABLE 11. SPDT TOGGLE SWITCH SW1, SW2, SW3 SPDT center open switches. Controls logic input RS, RC, PD. TABLE 4. TRANSHYBRID CIRCUIT R6, R7, R8, C7, U2 Transhybrid balance circuit cancels the input signal (that being received by the SLIC) from the transmit signal (that being transmitted from the SLIC). C7 couples the output of the SLIC to the transhybrid op-amp. It also provides the proper phase shift to account for C4’s phase shift. TABLE 5. FILTER CAPACITORS C1, C2 C1 is required for proper operation of the loop current limit function. C2 Filters out the AC to avoid false ring trip detection when ringing the phone. 4 TABLE 12. LOGIC TERMINAL PORT I/O Port This port allows external processor control of the 3 logic inputs (RS, RC, PD) and the logic output (SHD). SW1, SW2, SW3 need to be in the center open position for proper operation. Application Note 9736 HC5503 SLIC Operating Modes TABLE 13. DETECTOR (VALID) RS RC PD MODE 1 0 0 Power Denial 1 0 1 RD Active (Ringing) 1 1 0 Power Denial 1 1 1 Normal Loop Feed SHD ✓ ✓ RS is the ring synchronization input. RS is used to activate and deactivate the ring relay (K1) when the instantaneous ring voltage is near zero. If synchronization is not required the pin should be tied to +5V. HC5503 Evaluation Board Parts List COMPONENT SLIC VALUE U1 TOLERANCE RATING HC5503 COMPONENT VALUE TOLERANCE RATING C5, C6 0.01µF 20% 100V R1, R4 10.0kΩ 1% 1/4W C8, C11 0.1µF 20% 50V R2 24.9kΩ 1% 1/4W C9, C10 0.01µF 20% 50V R3 1.0kΩ 5% 1/4W CS1, CS2 0.1µF 20% 100V R5 510Ω 5% 1/4W D1, D2, D3, D4, D5 1N40007 n/a 100V, 1A R7 200kΩ 1% 1/4W D6 LED, RED n/a n/a R6, R8 150kΩ 1% 1/4W PTC Shorted n/a n/a RB1, RB2 150Ω 1% 2W MOV1, MOV2 Open n/a n/a RS1, RS2 1.0kΩ 1% 1/4W U2 C1 0.33µF 20% 50V RELAY (K1A,B) n/a n/a C2, C3, C4, C7 0.47µF 20% 50V SW1, SW2, SW3 5 CA741C Op-Amp DS2E-MDC5V SPDT CO PC Mount Switch HC5503/24 Evaluation Board Schematic Diagram +5V R5 I/O PORT +5V R4 R3 SHD PD RS RC D6 C8 H 6 SW1 SW2 L SW3 R6 16 RS1 CS1 D5 18 PD SHD K1 9 2 19 RS C9 7 6 VO 3 RC U2 R8 10 4 R7 C10 RD 2 K1A RB1 C7 TIP TIP FEED 11 RX HC5503 D2 MOV1 D1 D4 D3 MOV2 C 25 3 R1 VRX U1 VB-24V R2 (PINOUT FOR PLCC) 12 K1B CS2 TX RING FEED RING FEED SENSE 4 C1 28 C4 VTX 6 RS2 RB2 RING -BAT VBAT + 90VRMS BGND 13 26 14 DGND 7 AGND 27 VCC 5 PTC VB-24V RINGING C2 3 RING C11 -5V C5 C6 VB+ +5V C2 C1 Application Note 9736 TIP Application Note 9736 HC5503 Evaluation Board Layout SILK SCREEN TOP SIDE 7 Application Note 9736 HC5503 Evaluation Board Layout (Continued) BOTTOM SIDE All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. 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