19-2299; Rev 0; 1/02 ADSL Drivers/Receivers for Customer Premise Equipment Features ♦ Low-Noise Driver 4.8nV/√Hz Voltage-Noise Density 1.5pA/√Hz Current-Noise Density ♦ Full-Rate ADSL ATU-R Line Drivers and Receivers ♦ Single 5V Supply ♦ -75dBc SFDR at Full Output Power at 100kHz ♦ -95dB Driver-to-Receiver Crosstalk (MAX4363) The MAX4361 is a differential IN/differential OUT driver with a fixed gain of 3.1V/V. The MAX4362 is a dual amplifier with shutdown intended for use as a differential IN/differential OUT driver with gain set with external resistors. The MAX4363 is a quad amplifier with shutdown intended for use as a differential IN/differential OUT driver/receiver combination with gain set with external resistors. ♦ +12.5dBm Average Line Power (DMT) ♦ 280mA (min) Peak Output Current ♦ Rail-to-Rail® Output Swing ♦ Thermal and Short-Circuit Protection Ordering Information The MAX4361 is offered in a space-saving 8-pin µMAX package. TEMP RANGE PIN-PACKAGE MAX4361EUA PART -40°C to +85°C 8 µMAX MAX4361ESA -40°C to +85°C 8 SO ADSL Line Interface MAX4362EUB -40°C to +85°C 10 µMAX HDSL Line Driver MAX4362ESD -40°C to +85°C 14 SO MAX4363EUP -40°C to +85°C 20 TSSOP MAX4363ESP -40°C to +85°C 20 SO Applications Pin Configurations TOP VIEW GND 1 8 OUT+ T1IN+ 1 IN+ 2 7 V+ MAX4361 IN- 3 6 V+ T1IN- 2 SHDN 3 10 GND MAX4362 9 T1OUT 8 V+ N.C. 1 4 7 T2OUT 5 OUT- T2IN+ 5 6 GND µMAX/SO µMAX 20 GND (TX) 19 T1OUT T1IN+ 2 13 GND T1IN- 3 12 T1OUT SHDN 3 11 V+ T2IN- 4 17 T2OUT T2IN+ 5 16 GND (TX) MAX4362 T2IN- 5 GND 4 T1IN+ 1 T1IN- 2 SHDN 4 T2IN- 14 N.C. 10 T2OUT T2IN+ 6 9 GND N.C. 7 8 N.C. SO 18 V+ (TX) MAX4363 15 N.C. GND 6 R1IN+ 7 14 V+ (RX) R1IN- 8 13 GND (RX) R2IN- 9 12 R1OUT R2IN+ 10 11 R2OUT SO/TSSOP Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX4361/MAX4362/MAX4363 General Description The MAX4361/MAX4362/MAX4363 are a family of highperformance ADSL drivers and drivers/receivers ideal for the upstream transmit path and the downstream receive path of customer premise equipment. These devices operate from a single 5V supply and deliver up to 12.5dBm average line power for DMT modulated signals, meeting the requirements of full-rate ADSL. Spurious-free dynamic range (SFDR) at full output power is typically -75dBC at 100kHz. MAX4361/MAX4362/MAX4363 ADSL Drivers/Receivers for Customer Premise Equipment ABSOLUTE MAXIMUM RATINGS Supply Voltage (V+ to GND) ....................................-0.3V to +6V Analog Input Voltage .......................(GND - 0.3V) to (V+ + 0.3V) SHDN Input Voltage.........................(GND - 0.3V) to (V+ + 0.3V) Output Short-Circuit Duration .................................................10s Driver Output Current...............................................................1A Receiver Output Current ...................................................150mA Continuous Power Dissipation (TA = +70°C) 8-Pin µMAX (derate 4.5mW/°C above +70°C) ..............362mW 10-Pin µMAX (derate 5.6mW/°C above +70°C) ............444mW 8-Pin SO (derate 5.88mW/°C above +70°C).................471mW 14-Pin SO (derate 8.33mW/°C above +70°C)...............667mW 20-Pin SO (derate 10.0mW/°C above +70°C)...............800mW 20-Pin TSSOP (derate 10.9mW/°C above +70°C) ........879mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS—Driver (V+ = 5V, GND = 0, VCM = 2.5V, RL = 12.5Ω, SHDN = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values specified at TA = +25°C.) PARAMETER SYMBOL Supply Voltage Range (Note 1) VCC CONDITIONS MIN MAX4361, RL = ∞ MAX4362, RL = ∞ Supply Current IQ MAX4363, measured at V+ (TX), RL = ∞ MAX4363, measured at V+ (RX), RL = ∞ Maximum Average Output Power (Notes 2, 3) Gain G 22 MAX UNITS 5.5 V 33 mA mA SHDN = 0 22 33 SHDN = 5V 60 200 µA SHDN = 0 22 33 mA SHDN = 5V 60 200 µA SHDN = 0 4 6.5 mA SHDN = 5V 70 200 µA DMT modulation 15.5 CAP modulation 18 MAX4361 (0.7V ≤ VOUT ≤ (V+) - 0.7V) 3.0 3.1 dBm 3.2 V/V MAX4362/MAX4363 (0.7V ≤ VOUT ≤ (V+) - 0.7V) 68 81 dB Second Harmonic Distortion (Notes 3, 4) G = 3.1, f = 100kHz, VOUT(DIFF) = 7.1VP-P -66 -76 dBc Third Harmonic Distortion (Notes 3, 4) G = 3.1, f = 100kHz, VOUT(DIFF) = 7.1VP-P -68 -79 dBc Inferred from Output Voltage Swing test 280 Open-Loop Gain AVOL Peak Output Current IOUT Input Offset Voltage VOS Input Bias Current Input Offset Current Differential Input Resistance 2 POUT TYP 4.5 IB IOS RIN(DIFF) 330 ±0.5 mA ±10 mV µA 1.6 4.5 MAX4361 ±30 ±600 MAX4362/MAX4363 ±10 ±500 nA MAX4361 25 MΩ MAX4362/MAX4363 40 kΩ _______________________________________________________________________________________ ADSL Drivers/Receivers for Customer Premise Equipment (V+ = 5V, GND = 0, VCM = 2.5V, RL = 12.5Ω, SHDN = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values specified at TA = +25°C.) PARAMETER SYMBOL Input Common-Mode Voltage Range VCM CONDITIONS Inferred from CMRR test Common-Mode Rejection Ratio CMRR 1.25V ≤ VCM ≤ 4.5V Power-Supply Rejection Ratio PSRR V+ = 4.5V to 5.5V AC Power-Supply Rejection Ratio PSRRAC Differential Output-Voltage Swing (Note 4) VOUT(DIFF) f = 100kHz Output-Voltage Swing (Note 4) VOH, VOL MAX4362/MAX4363 RL = 12.5Ω MAX4361, RL = 12.5Ω, TA = -20°C to 85°C Output Short-Circuit Current Output Resistance SHDN Logic Low MAX4361 60 73 MAX4362/MAX4363 70 85 MAX4361 60 89 MAX4362/MAX4363 60 74 MAX4361 63 MAX4362/MAX4363 49 7.4 Shutdown Output Impedance IIH, IIL ZOUT(SD) 4.50 V dB dB dB VP-P 215 550 VOL 230 550 (V+) - VOH 400 600 VOL 430 650 (V+) - VOH 400 600 VOL 430 650 ±650 MAX4361 Ω 0.001 0.8 V ±10 µA 2.0 V SHDN = 0 or SHDN = V+ f = 1MHz mV mA 0.3 MAX4362/MAX4363, G = 1 VIH SHDN Input Current UNITS 8.2 VIL SHDN Logic High MAX (V+) - VOH ISC ROUT TYP 1.25 Inferred from Output Voltage Swing test RL = 100Ω MIN 1.8 kΩ MAX4361 40 MAX4362/MAX4363, G = 1 60 SR VOUT(DIFF) = 7.1VP-P step 30 Settling Time (1%) tS VOUT(DIFF) = 7.1VP-P step Voltage-Noise Density en f = 100kHz to 1.1MHz 4.8 nV/√Hz Current-Noise Density in f = 100kHz to 1.1MHz 1.5 pA/√Hz 10 nF tSHDN 400 ns tENABLE 2.8 µs -3dB Bandwidth BW Slew Rate Capacitive-Load Stability Shutdown Delay Time Enable Delay Time MAX4361 115 MAX4362/MAX4363, G=3 165 MHz V/µs ns _______________________________________________________________________________________ 3 MAX4361/MAX4362/MAX4363 ELECTRICAL CHARACTERISTICS—Driver (continued) MAX4361/MAX4362/MAX4363 ADSL Drivers/Receivers for Customer Premise Equipment ELECTRICAL CHARACTERISTICS—Receiver (MAX4363 only) (V+ = 5V, GND = 0, VCM = 2.5V, RL = ∞, SHDN = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values specified at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN MAX UNITS SFDR Gain-Bandwidth Product GBW Open-Loop Gain AVOL 1.5V ≤ VOUT ≤ 3.5V Peak Output Current IOUT RL = 50Ω, inferred from Output-Voltage Swing test Input Offset Voltage VOS ±0.5 ±10 IB -0.75 -2 µA IOS ±20 ±250 nA CIN 1.6 pF RIN(DIFF) 76 kΩ Input Bias Current Input Offset Current Input Capacitance Differential Input Resistance Input Common-Mode Voltage Range VCM G = 1, f = 1MHz, VOUT = 1VP-P TYP Spurious-Free Dynamic Range Inferred from CMRR test -75 dBc 190 MHz 65 77 dB 18 25 mA 0.25 3.80 mV V Common-Mode Rejection Ratio CMRR 0.25V ≤ VCM ≤ 3.8V 70 87 dB Power-Supply Rejection Ratio PSRR V+ = 4.5V to 5.5V 60 75 dB 47 dB AC Power-Supply Rejection Ratio PSRRAC f = 1MHz RL = ∞ Output-Voltage Swing VOH, VOL RL = 50Ω Output Short-Circuit Current (V+) - VOH 0.64 1 VOL 0.73 1 (V+) - VOH 1.27 1.5 1.37 1.6 VOL ±130 ISC V mA 0.001 Ω Slew Rate SR VOUT = 1VP-P step 160 V/µs Settling Time (1%) tS VOUT = 100mVP-P step, G = 1 40 ns Voltage-Noise Density en f = 1MHz 8.5 nV/√Hz Current-Noise Density in f = 1MHz 0.5 pA/√Hz f = 100kHz 95 dB Output Resistance Driver-Receiver Crosstalk ROUT XTALK G=1 Note 1: Guaranteed by the Power-Supply Rejection Ratio (PSRR) test. Note 2: Implied by worst-case output-voltage swing (VOUT(DIFF)), crest factor (Cr) and load resistance (RL): PDriver = 10log((250 ✕ (VOUT(DIFF) )^2 / ((Cr)^2 ✕ RL)) dBmW Note 3: Guaranteed by design. Note 4: May exceed absolute maximum ratings for power dissipation if unit is subject to full-scale sinusoids for long periods (see Applications Information section). 4 _______________________________________________________________________________________ ADSL Drivers/Receivers for Customer Premise Equipment DRIVER DIFFERENTIAL DISTORTION vs. PEAK-TO-PEAK OUTPUT VOLTAGE -60 2ND HARMONIC -70 3RD HARMONIC -80 -90 100k 10k 3RD HARMONIC -70 -80 2ND HARMONIC -90 3RD HARMONIC -80 2ND HARMONIC -90 3 4 5 6 7 8 5 25 45 65 85 PEAK-TO-PEAK OUTPUT VOLTAGE (V) RLOAD (Ω) DRIVER LINE POWER vs. TURNS RATIO DRIVER CURRENT AND VOLTAGE NOISE vs. FREQUENCY DRIVER OUTPUT IMPEDANCE vs. FREQUENCY 13.5 13.0 12.5 12.0 V+ = 4.5V 11.5 11.0 10.5 10.0 10 10 VNOISE 10k INOISE 1 1k 10k 100k SHDN = VCC 1k 100 10 1 SHDN = GND 0.1 1 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 MAX4361 toc06 100k OUTPUT IMPEDANCE (Ω) V+ = 5V 100 INPUT VOLTAGE NOISE (nV/√Hz) INPUT CURRENT NOISE (pA/√Hz) 14.0 MAX4361 toc05 100 MAX4361 toc04 V+ = 5.5V 0.01 1M 1M 100k 10M 100M FREQUENCY (Hz) DRIVER GAIN AND PHASE vs. FREQUENCY DRIVER POWER-SUPPLY REJECTION RATIO vs. FREQUENCY DRIVER OUTPUT SWING vs. LOAD RESISTANCE GAIN 5 10 90 0 60 -10 30 0 0 -5 -30 PHASE -20 -30 -40 -10 -60 -15 -90 -20 -120 -60 -25 -150 -70 -180 -80 -30 100k 1M 10M FREQUENCY (Hz) 100M 1G G=1 OUTPUT SWING (V) 10 120 PSRR (dB) 15 PHASE (DEGREES) MAX4361 toc07 G=3 RL = 12.5Ω -50 1k 10k 100k 1M FREQUENCY (Hz) 10M 1G 2.5 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 MAX4361 toc09 FREQUENCY (Hz) MAX4361 toc08 TRANSFORMER TURNS RATIO 20 10k -70 -100 2 1M MAX4361 toc03 MAX4361 toc02 -60 VOUT = 5VP-P f = 100kHz G=3 RL = 12.5Ω FREQUENCY (Hz) 16.0 15.5 15.0 14.5 PLINE (dBm) -60 -100 -100 GAIN (dB) f = 100kHz G=3 RL = 12.5W -50 DIFFERENTIAL DISTORTION (dBc) VOUT = 7.2VP-P G=3 RL = 12.5Ω -50 -40 MAX4361 toc01 DIFFERENTIAL DISTORTION (dB) -40 DRIVER DIFFERENTIAL DISTORTION vs. LOAD RESISTANCE DIFFERENTIAL DISTORTION (dBc) DRIVER DIFFERENTIAL DISTORTION vs. FREQUENCY +SWING -SWING 1 10 100 1k 10k LOAD RESISTANCE (Ω) _______________________________________________________________________________________ 5 MAX4361/MAX4362/MAX4363 Typical Operating Characteristics (V+ = 5V, GND = 0, VCM = 2.5V, RL = 12.5Ω, SHDN = 0, TA = +25°C.) Typical Operating Characteristics (continued) (V+ = 5V, GND = 0, VCM = 2.5V, RL = 12.5Ω, SHDN = 0, TA = +25°C.) -60 2ND HARMONIC -70 3RD HARMONIC -90 60 -100 VNOISE 10 1 10 1 INOISE 0.1 1M 100k 1k 10k 0 20 -30 -60 10 0 -120 -20 -150 -30 -180 10k 1M 100k -20 -30 -40 -50 -20 -40 -60 RL = 12.5Ω -80 10M 100M 1G RECEIVER-TO-RECEIVER CROSSTALK vs. FREQUENCY 0 CROSSTALK (dB) -10 1M FREQUENCY (Hz) 0 MAX4361 toc14 G=1 -90 PHASE -10 DRIVER-TO-RECEIVER CROSSTALK vs. FREQUENCY MAX4361 toc13 10 30 30 FREQUENCY (Hz) RECEIVER POWER-SUPPLY REJECTION RATIO vs. FREQUENCY 0 100k 60 GAIN 40 0.1 FREQUENCY (Hz) -20 -40 RL = 150Ω -60 NO LOAD -80 -60 -100 -100 -70 NO LOAD -80 -120 1k 10k 100k 1M 10M 100M -120 10k 100k FREQUENCY (Hz) 1M 10M 100M 1G FREQUENCY (Hz) 10k 100k 1M RF = 1kΩ MAX4361 toc16 4 RF = 500Ω GAIN (dB) 0 -2 RF = 100Ω -4 -6 G = -1 RL = 150Ω VP-P = 100mV -8 -10 10k 100k 1M 10M 100M 1G FREQUENCY (Hz) 6 10M FREQUENCY (Hz) RECEIVER OUTPUT AMPLITUDE vs. FREQUENCY 2 90 50 CROSSTALK (dB) 10k 120 G = 1000 RL = 500Ω MAX4361 toc15 -80 MAX4361 toc12 70 100 GAIN (dB) -50 MAX4361 toc11 100 INPUT VOLTAGE NOISE (nV/√Hz) VOUT = 1VP-P G=1 RL = 150Ω INPUT CURRENT NOISE (pA/√Hz) MAX4361 toc010 DIFFERENTIAL DISTORTION (dB) -40 RECEIVER GAIN AND PHASE vs. FREQUENCY RECEIVER CURRENT AND VOLTAGE NOISE vs. FREQUENCY _______________________________________________________________________________________ 100M 1G PHASE (DEGREES) RECEIVER DIFFERENTIAL DISTORTION vs. FREQUENCY PSRR (dB) MAX4361/MAX4362/MAX4363 ADSL Drivers/Receivers for Customer Premise Equipment ADSL Drivers/Receivers for Customer Premise Equipment MAX4361 PIN NAME 1, 4 GND Ground FUNCTION 2 IN+ First Driver Input 3 IN- Second Driver Input 5 OUT- 6, 7 V+ 8 OUT+ Second Driver Output Positive Power-Supply Voltage. Bypass V+ to GND with a 0.1µF capacitor. First Driver Output MAX4362 PIN NAME FUNCTION µMAX SO 1 2 T1IN+ First Driver Noninverting Input 2 3 T1IN- First Driver Inverting Input 3 4 SHDN Shutdown. Connect to GND for normal operation. 4 5 T2IN- Second Driver Inverting Input 5 6 T2IN+ Second Driver Noninverting Input 6, 10 9, 13 GND Ground 7 10 T2OUT 8 11 V+ 9 12 T1OUT — 1, 7, 8, 14 N.C. Second Driver Output Positive Power-Supply Voltage. Bypass V+ to GND with a 0.1µF capacitor. First Driver Output No Connection. Not internally connected. _______________________________________________________________________________________ 7 MAX4361/MAX4362/MAX4363 Pin Descriptions MAX4361/MAX4362/MAX4363 ADSL Drivers/Receivers for Customer Premise Equipment Pin Descriptions (continued) MAX4363 PIN NAME 1 T1IN+ First Driver Noninverting Input 2 T1IN- First Driver Inverting Input 3 SHDN Shutdown. Connect to GND for normal operation. 4 T2IN- Second Driver Inverting Input 5 T2IN+ Second Driver Noninverting Input 6 GND Ground 7 R1IN+ First Receiver Noninverting Input 8 R1IN- First Receiver Inverting Input 9 R2IN- Second Receiver Inverting Input 10 R2IN+ Second Receiver Noninverting Input 11 R2OUT Second Receiver Output 12 R1OUT First Receiver Output 13 GND (RX) 14 V+ (RX) FUNCTION Ground for Receiver Amplifiers Positive Power-Supply Voltage for Receiver Amplifiers. Bypass V+ (RX) to GND (RX) with a separate 0.1µF capacitor. 15 N.C. 16, 20 GND (TX) No Connection. Not internally connected. 17 T2OUT Second Driver Output 18 V+ (TX) Positive Power-Supply Voltage for Driver Amplifiers. Bypass V+ (TX) to GND (TX) with a separate 0.1µF capacitor. 19 T1OUT First Driver Output Ground for Driver Amplifier Detailed Description The MAX4361/MAX4362/MAX4363 are a family of highperformance ADSL drivers and drivers/receivers ideal for the upstream transmit path and the downstream receive path of customer premise equipment. These devices operate from a single 5V supply and deliver up to 12.5dBm average line power for DMT modulated signals, meeting the requirements of full-rate ADSL. SFDR at full output power is typically -75dBc at 100kHz. Differential In/Differential Out ADSL Driver (MAX4361) The MAX4361 is a differential line driver with a fixed gain of 3.1V/V. The gain is set by three internal resistors. 8 Uncommitted Dual Amplifier for ADSL Driver (MAX4362) The MAX4362 is a dual amplifier with shutdown intended for use as a differential IN/differential OUT driver with gain set with external resistors Uncommitted Quad Amplifier for ADSL Driver/Receiver (MAX4363) The MAX4363 is a quad amplifier with shutdown intended for use as a differential IN/differential OUT driver/receiver combination with gain set with external resistors. Shutdown The MAX4362/MAX4363 feature a low-power shutdown mode. When the SHDN pin is pulled high, the supply current drops to 70µA, and the amplifier’s outputs are placed in a high-impedance disable mode. Connect SHDN to GND for normal operation. _______________________________________________________________________________________ ADSL Drivers/Receivers for Customer Premise Equipment 500Ω 1kΩ Power Supply and Decoupling The MAX4361/MAX4362/MAX4363 should be powered from a well-regulated, low-noise, 4.5V to 5.5V supply in order to optimize the ADSL upstream drive capability to +12.5dBm and maintain the best SFDR. High-quality capacitors with low equivalent series resistance (ESR) such as multilayer ceramic capacitors (MLCCs) should be used to minimize supply voltage ripple and power dissipation. A larger capacitor located in proximity to the MAX4361/MAX4362/MAX4363 improves decoupling for lower frequency signals. In addition, 0.1µF MLCC decoupling capacitors should be located as close as possible to each of the powersupply pins, no more than 1/8 inch away. An additional large (4.7µF to 10µF) tantalum capacitor should be placed on the board near the supply terminals to supply current for fast, large-signal changes at the MAX4361/MAX4362/MAX4363 outputs. MAX4361/MAX4362 The MAX4361/MAX4362 require a single 0.1µF bypass from V+ to ground located as close as possible to the IC leads. MAX4363 The MAX4363 features separate supply and ground pins for the receiver and driver amplifiers. Bypass the V+ (RX) supply to the GND (RX) pin with a 0.1µF capacitor. Bypass the V+ (TX) supply to the GND (TX) pin with a separate 0.1µF capacitor. Both capacitors should be placed as close as possible to their respective IC leads. USB Applications The 5V supplied at the universal serial bus (USB) port may be poorly regulated or unable to supply the peak currents required by an ADSL modem. Improving the quality of the supply will optimize the performance of the MAX4361/MAX4362/MAX4363 in a USB-supplied CPE ADSL modem. This can be accomplished through the use of a step-up DC-to-DC converter or switching power supply followed by a low-dropout (LDO) regulator. Careful attention must be paid to decoupling the power supply at the output of the DC-to-DC converter, the output of the LDO regulator and the supply pins of the MAX4361/MAX4362/MAX4363. Driving a Capacitive Load The MAX4361/MAX4362/MAX4363 are capable of driving capacitive loads up to 2nF. Most hybrid circuits are well under this limit. For additional capacitive-drive capability use isolation resistors between the output 3.1Ω OUTPUT MAX436 _ CLOAD INPUT Figure 1. Driving Capacitive Load 5V R1 2.7kΩ VREF R2 2.7kΩ 0.1µF Figure 2. Voltage-Divider Reference and the load to reduce ringing on the output signal. In a typical hybrid the back-matching resistors provide sufficient isolation for most any capacitive-loading condition (see Figure 1). Method for Generating a Midsupply Voltage To operate an amplifier on a single-voltage supply, a voltage midway between the supply and ground must be generated to properly bias the inputs and the outputs. A voltage divider can be created with two equal-value resistors (Figure 2). There is a trade-off between the power consumed by the divider and the voltage drop across these resistors due to the positive input bias currents. Selecting 2.7kΩ for R1 and R2 will create a voltage divider that draws less than 1mA from a 5V supply. Use a decoupling capacitor (0.1µF) at the node where VREF is generated. Power Dissipation It is important to consider the total power dissipation of the MAX4361/MAX4362/MAX4363 in order to properly size the heat sink area of an application. With some simplifying assumptions we can estimate the total power dissipated in the driver (see Typical Operating _______________________________________________________________________________________ 9 MAX4361/MAX4362/MAX4363 Applications Information Circuit). If the output current is large compared to the quiescent current, computing the dissipation in the output devices and adding it to the quiescent power dissipation will give a close approximation of the total power dissipation in the package. For a 12.5dBm average line power on a 100Ω line, the RMS current is 13.4mA. With a one-to-four transformer the driver therefore supplies 53.6mA RMS. It can be shown for a DMT signal the ratio of RMS current to the average rectified current is 0.8. The total power consumption is approximately PCONS = 0.8 ✕ 53.6 x 5V = 214mW of which 18mW is delivered as line power and 18mW is dissipated in the back-matching resistors. Hence the average power consumption of the IC is approximately 178mW + quiescent power (110mW), or 288mW. For the MAX4361 in an 8-pin µMAX package, this corresponds to a temperature rise of 64°C. With an ambient temperature of +85°C this corresponds to a junction temperature of +148°C, just below the absolute maximum of +150°C. Please note the part is capable of over 200mA RMS, which could cause thermal shutdown in applications with elevated ambient temperatures and/or signals with low crest factors. See Figure 3 for a guide to power derating for each of the MAX4361/MAX4362/MAX4363 packages. Transformer Selection Full-rate, customer premise ADSL requires the transmission of a +12.5dBm (18mW) DMT signal. The DMT signal has a typical crest factor of 5.3, requiring the line driver to provide peak line power of 27.5dBm (560mW). The 27.5dBm peak line power translates into a 28.4V peak-to-peak differential voltage on the 100Ω telephone line. The maximum low-distortion output swing available from the MAX4361/MAX4362/MAX4363 line driver on a 5V supply is 3.8V and, taking into account the power lost due to the back-matching resistance, a step-up transformer with turns ratio of 3.8 or greater is needed. In the Typical Operating Circuit, the MAX4363 is coupled to the phone line through a step-up transformer with a 1:4 turns ratio. R1 and R2 are back-matching resistors, each 3.1Ω (100Ω / (2 ✕ 42)), where 100Ω is the approximate phone-line impedance. The total differential load for the MAX4361/MAX4362/MAX4363, including the termination resistors, is therefore 12.5Ω. Even under these conditions the MAX4361/MAX4362/ MAX4363 provide low distortion signals to within 0.6V of the power rails. 10 2.5 MAXIMUM POWER DISSIPATION (W) MAX4361/MAX4362/MAX4363 ADSL Drivers/Receivers for Customer Premise Equipment MAX4362 14-PIN SO 2.0 MAX4363 20-PIN SO MAX4363 20-PIN TSSOP 1.5 1.0 0.5 0 MAX4361 8-PIN µMAX MAX4362 10-PIN µMAX -40 -20 0 20 MAX4361 8-PIN SO 40 60 80 TEMPERATURE (°C) Figure 3. Maximum Power Dissipation vs. Temperature Receive Channel Considerations A transformer used at the output of the differential line driver to step up the differential output voltage to the line has the inverse effect on signals received from the line. A voltage reduction or attenuation equal to the inverse of the turns ratio is realized in the receive channel of a typical bridge hybrid. The turns ratio of the transformer may also be dictated by the ability of the receive circuitry to resolve low-level signals in the noisy, twisted-pair telephone plant. Higher turns-ratio transformers effectively reduce the received signal-to-noise ratio due to the reduction in the received signal strength. The MAX4363 includes an amplifier with typical voltage noise of only 8.5nV/√Hz and a low-supply current of 2mA/amplifier to be used as the receive channel. Layout Considerations Good layout techniques optimize performance by decreasing the amount of stray capacitance at the amplifier’s inputs and outputs. Excess capacitance will produce peaking in the amplifier’s frequency response. To decrease stray capacitance, minimize trace lengths by placing external components as close to the amplifier as possible. Chip Information MAX4361 TRANSISTOR COUNT: 1400 MAX4362 TRANSISTOR COUNT: 1400 MAX4363 TRANSISTOR COUNT: 1750 PROCESS: Bipolar ______________________________________________________________________________________ ADSL Drivers/Receivers for Customer Premise Equipment 5V 0.1µF 5V 1kΩ 2.7kΩ 1kΩ 0.1µF 2.7kΩ 10kΩ VCC 3.125Ω 0.047µF IN1+ OUT+ IN10.047µF 10kΩ 1kΩ DRIVER LINE IMPEDANCE IN2- 3.125Ω 100Ω OUT- IN2+ 1:4 TRANSFORMER ADSL CHIPSET 500Ω 1kΩ MAX4363 1kΩ 5V 500Ω OUT+ IN1IN1+ IN2+ OUT- RECEIVER IN25V 10kΩ GND 1kΩ 0.1µF 10kΩ 1kΩ ______________________________________________________________________________________ 11 MAX4361/MAX4362/MAX4363 Typical Operating Circuit ADSL Drivers/Receivers for Customer Premise Equipment 10LUMAX.EPS 8LUMAXD.EPS MAX4361/MAX4362/MAX4363 Package Information 12 ______________________________________________________________________________________ ADSL Drivers/Receivers for Customer Premise Equipment SOICN.EPS Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX4361/MAX4362/MAX4363 Package Information (continued)