19-2339; Rev 1; 3/02 KIT ATION EVALU E L B A AVAIL Upstream CATV Amplifier ♦ Single 3.3V Supply Operation ♦ Accurate Gain Control, ±1dB over 53dB Range ♦ Gain Programmable in 0.5dB Steps ♦ -55dBc Harmonic Distortion at 65MHz ♦ Low Burst On/Off Transient ♦ High Efficiency: 182mW at 34dBmV Out; 16mW in Transmit-Disable Mode Ordering Information PART TEMP RANGE PIN-PACKAGE MAX3503EGP -40°C to +85°C 20 QFN-EP* (5mm × 5mm) *Exposed pad. ________________________Applications CEXT GND 16 N.C. N.C. N.C. 17 GND 19 Telephony Over Cable TOP VIEW N.C. OpenCable Set-Top Box Pin Configuration 20 DOCSIS/EuroDOCSIS and DVB Cable Modems 18 The MAX3503 is available in a 20-pin QFN package. The device operates in the extended industrial temperature range (-40°C to +85°C). Features CATV Status Monitor VCC 1 15 VCC IN+ 2 14 OUT+ GND 3 13 N.C. IN- 4 12 OUT- GND 5 11 N.C. 8 9 10 TXEN SHDN 7 SCLK CS 6 SDA GND MAX3503 GND Typical Operating Circuit appears at end of data sheet. QFN** SPI is a trademark of Motorola, Inc. DOCSIS/EuroDOCSIS/OpenCable are trademarks of CableLabs®. **NOTE: CORNER GND PINS AND THE EXPOSED PAD MUST BE SOLDERED TO THE SUPPLY GROUND. ________________________________________________________________ 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 MAX3503 General Description The MAX3503 programmable power amplifier is designed for use in CATV upstream applications. The MAX3503 drives 61dBmV (QPSK) into a 75Ω load when driven with a 34dBmV nominal input signal. Both input and output ports are differential, requiring that an external balun be used at the output port. The variable gain feature provides greater than 56dB of dynamic range, which is controlled by an SPI™ 3-wire interface. Gain control is available in 0.5dB steps. The device operates over a frequency range of 5MHz to 65MHz. The MAX3503 is internally matched for use with a 1:1 balun. This device operates from a single 3.3V DC supply and draws 235mA during transmit (100% duty cycle, 61dBmV out). The bias current is automatically adjusted, based on the output level to increase efficiency. Additionally, the device can be disabled between bursts to minimize noise and save power while maintaining a match at the output port. A shutdown mode is available to disable all circuitry and reduce current consumption to 5µA (typ). MAX3503 Upstream CATV Amplifier ABSOLUTE MAXIMUM RATINGS VCC, OUT+, OUT-..................................................-0.5V to +6.5V Input Voltage Levels (all inputs) .................-0.3V to (VCC + 0.3V) Continuous Input Voltage (IN+, IN-)....................................2VP-P Continuous Current (OUT+, OUT-) ...................................175mA Continuous Power Dissipation (TA = +85°C) 20-Pin QFN (derate 27mW/°C above +85°C) .............1600mW 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. DC ELECTRICAL CHARACTERISTICS (MAX3503 EV kit, VCC = 3.1V to 3.6V, VGND = 0, TXEN = SHDN = high, TA = -40°C to +85°C. Typical parameters are at VCC = 3.3V, TA = +25°C, unless otherwise specified.) (Note1) PARAMETER SYMBOL Supply Voltage VCC Supply-Current Transmit Mode ICC Supply-Current Transmit Disable Mode Supply-Current Low-Power Standby CONDITIONS MIN TYP 3.1 D7 = 1, gain code = 115 (Av = 27dB) 235 D7 = 0, gain code = 92 (Av = 0dB) 55 ICC TXEN = low 4.8 ICC SHDN = low 5 MAX UNITS 3.6 V 287 7 mA mA µA LOGIC INPUTS Input High Voltage VINH Input Low Voltage VINL 2 Input High Current IBIASH VINH = VCC Input Low Current IBIASL VINL = 0V V 0.8 V 100 µA -100 µA AC ELECTRICAL CHARACTERISTICS (MAX3503 EV kit, VCC = 3.1V to 3.6V, VGND = 0, PIN = 34dBmV, TXEN = SHDN = high, TA = -40°C to +85°C. Typical parameters are at TA = +25°C, unless otherwise specified.) (Note 1) PARAMETER Voltage Gain, fIN = 5MHz Voltage Gain, fIN = 65MHz 2 SYMBOL AV AV MIN TYP MAX D7 = 1, gain code = 119, TA = 0°C to +85°C CONDITIONS 27 28.5 30 D7 = 1, gain code = 99, TA = 0°C to +85°C 17 18.5 20 D7 = 1, gain code = 83, TA = 0°C to +85°C 9 10.5 12 D7 = 0, gain code = 112, TA = 0°C to +85°C 8 9.5 11 D7 = 0, gain code = 92, TA = 0°C to +85°C -2 -0.5 1 D7 = 0, gain code = 72, TA = 0°C to +85°C -12 -10.5 -9 D7 = 0, gain code = 43, TA = 0°C to +85°C -26.5 -25 -23.5 D7 = 1, gain code = 119, TA = -40°C to +85°C (Note 2) 26.3 _______________________________________________________________________________________ UNITS dB dB Upstream CATV Amplifier (MAX3503 EV kit, VCC = 3.1V to 3.6V, VGND = 0, PIN = 34dBmV, TXEN = SHDN = high, TA = -40°C to +85°C. Typical parameters are at TA = +25°C, unless otherwise specified.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX VOUT = 61dBmV, fIN = 5MHz to 42MHz, (Note 2) -0.6 -1.2 VOUT = 61dBmV, fIN = 5MHz to 65MHz, (Note 2) -1.1 -1.9 fIN = 5MHz to 65MHz, AV = -26dB to 27dB 0.5 Gain Rolloff UNITS dB Gain Step Size fIN = 5MHz to 65MHz, AV = -26dB to 27dB, any 2-bit transition of D0, D1 0.7 1 1.3 fIN = 5MHz to 65MHz, D7 = 0, gain code = 112, to D7 = 1, gain code = 83 0.65 1 1.35 Transmit-Disable Mode Noise TXEN = low, BW = 160kHz, fIN = 5MHz to 65MHz (Note 2) Isolation in Transmit-Disable Mode TXEN = low, fIN = 5MHz to 65MHz (Note 2) Transmit Mode Noise BW = 160kHz, fIN = 5MHz to 65MHz, AV = -26dB to 27dB (Note 2) Transmit Enable Transient Duration Transmit Disable Transient Duration 60 dBmV dB -55 dBc TXEN input rise/fall time < 0.1µs, TA = +25°C (Note 2) 2 µs TXEN input rise/fall time < 0.1µs, TA = +25°C (Note 2) 2 µs D7 = 1, gain code = 115 (AV = 27dB), TA = +25°C Transmit Disable/Transmit Enable Transient Step Size -65 dB 30 D7 = 0, gain code = 83 (AV = 11dB), TA = -40°C to +85°C 80 20 mVP-P D7 = 0, gain code = 92 (AV = 0dB), TA = +25°C 3 fIN = 5MHz to 65MHz, differential (Note 2) 2 kΩ Output Return Loss fIN = 5MHz to 65MHz, in 75Ω system, D7 = 1, gain code = 119, (AV = 27dB) 10 dB Output Return Loss in TransmitDisable Mode fIN = 5MHz to 65MHz, in 75Ω system, TXEN = low 10 dB Input Impedance ZIN _______________________________________________________________________________________ 3 MAX3503 AC ELECTRICAL CHARACTERISTICS (continued) MAX3503 Upstream CATV Amplifier AC ELECTRICAL CHARACTERISTICS (continued) (MAX3503 EV kit, VCC = 3.1V to 3.6V, VGND = 0, PIN = 34dBmV, TXEN = SHDN = high, TA = -40°C to +85°C. Typical parameters are at TA = +25°C, unless otherwise specified.) (Note 1) PARAMETER Two-Tone Third-Order Distortion SYMBOL IM3 2nd Harmonic Distortion HD2 3rd Harmonic Distortion HD3 TYP MAX Input tones at 42MHz and 42.2MHz, both 31dBmV, VOUT = 58dBmV/tone (Note 2) CONDITIONS MIN -53 -47 Input tones at 65MHz and 65.2MHz, both 31dBmV, VOUT = 58dBmV/tone -49 fIN = 33MHz, VOUT = 61dBmV -55 -50 fIN = 65MHz, VOUT = 61dBmV (Note 2) -55 -50 fIN = 22MHz, VOUT = 61dBmV -55 -50 fIN = 65MHz, VOUT = 61dBmV -55 -50 UNITS dBc dBc dBc TIMING CHARACTERISTICS (VCC = 3.1V to 3.6V, VGND = 0V, TXEN = SHDN = high, D7 = 1, TA = +25°C, unless otherwise specified.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SEN-to-SCLK Rise Set Time tSENS 20 ns SEN-to-SCLK Rise Hold Time tSENH 10 ns SDA-to-SCLK Setup Time tSDAS 10 ns SDA-to-SCLK Hold Time tSDAH 20 ns SDA Pulse Width High TDATAH 50 ns SDA Pulse Width Low TDATAL 50 ns SCLK Pulse Width High tSCLKH 50 ns SCLK Pulse Width Low tSCLKL 50 ns Note 1: All parameters guaranteed by design and characterization to ±3 sigma for TA < +25°C, unless otherwise specified. Note 2: Guaranteed by design and characterization to ±6 sigma. 4 _______________________________________________________________________________________ Upstream CATV Amplifier 180 150 120 TRANSMIT-ENABLE MODE, LOW NOISE, GAIN CODE = 100 60 TRANSMIT-DISABLE MODE 0 -25 0 25 50 75 40 60 100 120 2.9 140 +25°C -27.0 -27.5 +85°C GAIN CODE = 119 28.8 28.6 VOLTAGE GAIN (dB) -40°C 28.4 VCC = 3.0V VCC = 3.3V 28.2 28.0 27.8 VCC = 3.6V 27.6 -8.2 -9.4 10 35 60 VOLTAGE GAIN vs. FREQUENCY HIGH-POWER MODE VOLTAGE GAIN vs. FREQUENCY LOW-NOISE MODE A VOLTAGE GAIN (dB) 20 B 15 10 C 5 10 0 A 0 GAIN CODE A = 119, B = 99, C = 82, D = 62 B C -20 -10 -15 1 10 D GAIN CODE A = 112, B = 92, C = 72, D = 43 -30 -40 100 FREQUENCY (MHz) 1000 1 10 100 FREQUENCY (MHz) 10 35 60 85 VOLTAGE GAIN vs. GAIN CODE -10 D -5 -15 TEMPERATURE (°C) 20 MAX3503 toc07 30 -40 85 VOLTAGE GAIN (dB) -15 MAX3503 toc08 -40 TEMPERATURE (°C) 25 VCC = 3.6V -9.6 SUPPLY VOLTAGE (V) 35 VOLTAGE GAIN (dB) 3.6 VCC = 3.0V -9.2 -9.8 3.5 3.6 VCC = 3.3V -9.0 -10.0 3.4 3.5 GAIN CODE = 80 -8.8 27.0 3.3 3.4 -8.6 -29.0 3.2 3.3 -8.4 27.2 3.1 3.2 -8.0 -28.5 3.0 3.1 VOLTAGE GAIN vs. TEMPERATURE LOW-NOISE MODE 27.4 2.9 3.0 SUPPLY VOLTAGE (V) 29.0 -26.0 VOLTAGE GAIN (dB) 80 VOLTAGE GAIN vs. TEMPERATURE HIGH-POWER MODE MAX3503 toc04 -25.5 MAX3503 toc03 26.0 20 GAIN CODE GAIN CODE = 43 -28.0 +85°C 26.5 VOLTAGE GAIN vs. SUPPLY VOLTAGE LOW-NOISE MODE -26.5 27.5 27.0 TEMPERATURE (°C) -25.0 28.0 LOW-NOISE MODE 0 100 +25°C 1000 35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 MAX3503 toc09 -50 HIGH-POWER MODE -40°C 28.5 VOLTAGE GAIN (dB) 30 29.0 MAX3503 toc05 90 GAIN CODE = 119 29.5 MAX3503 toc06 SUPPLY CURRENT (mA) SUPPLY CURRENT (mA) 210 30.0 MAX3503 toc02 TRANSMIT-ENABLE MODE, HIGH POWER, GAIN CODE = 119 240 390 360 330 300 270 240 210 180 150 120 90 60 30 0 VOLTAGE GAIN (dB) MAX3503 toc01 270 VOLTAGE GAIN vs. SUPPLY VOLTAGE HIGH-POWER MODE SUPPLY CURRENT vs. GAIN CODE SUPPLY CURRENT vs. TEMPERATURE HIGH-POWER MODE LOW-NOISE MODE 30 40 50 60 70 80 90 100 110 120 GAIN CODE _______________________________________________________________________________________ 5 MAX3503 Typical Operating Characteristics (Typical Application Circuit, VCC = 3.3V, VIN = 34dBmV, TXEN = SHDN = high, fIN = 20MHz, ZLOAD = 75Ω, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (Typical Application Circuit, VCC = 3.3V, VIN = 34dBmV, TXEN = SHDN = high, fIN = 20MHz, ZLOAD = 75Ω, TA = +25°C, unless otherwise noted.) GAIN STEP vs. GAIN CODE HIGH-POWER MODE GAIN STEP vs. GAIN CODE LOW-NOISE MODE 0.8 0.7 GAIN STEP (dB) 0.7 0.6 0.5 0.4 0.6 0.5 0.4 0.3 0.3 0.2 0.2 0.1 0.1 -25 -30 HIGH-POWER MODE -35 -40 -45 LOW-NOISE MODE -50 0.0 -55 70 80 90 100 110 30 120 70 80 90 100 110 120 30 -85 -90 50dBmV, HP -65 20dBmV, LN -70 6dBmV, LN -75 -80 20 30 40 50 60 70 10 20 30 40 50 INPUT FREQUENCY (MHz) OUTPUT RETURN LOSS vs. FREQUENCY (75Ω SYSTEM) OUTPUT IMPEDANCE (75Ω SYSTEM) LOW-NOISE MODE/ TRANSMITDISABLE MODE -10 HIGH-POWER MODE HIGH-POWER MODE LOW-NOISE MODE/ TRANSMIT-DISABLE MODE 60 70 LOW-NOISE MODE 0 20 40 60 80 0 -10 VOUT = 61dBmV α = 0.25 1280ksps -20 -30 -40 -50 -70 -80 -30 10 100 500kHz/div FREQUENCY (MHz) 6 120 140 OUTPUT SPECTRUM 10 -60 -25 100 GAIN CODE MAX3503 toc17 MAX3503 toc16 -5 1 0.1 0 INPUT FREQUENCY (MHz) 0 HIGH-POWER MODE 10 -85 -90 10 130 MAX3503 toc15 -60 100 (dB) -95 1 110 MAX3503 toc18 6dBmV, LN -55 61dBmV, HP TRANSIENT LEVEL (mVP-P) -80 -50 MAX3503 toc14 MAX3503 toc13 20dBmV, LN -20 90 POWER-UP/DOWN TRANSIENTS vs. GAIN CODE 50dBmV, HP -15 70 3RD HARMONIC DISTORTION vs. INPUT FREQUENCY 61dBmV, HP 0 50 2ND HARMONIC DISTORTION vs. INPUT FREQUENCY -60 -75 60 GAIN CODE -55 -70 50 GAIN CODE -50 -65 40 GAIN CODE 3RD HARMONIC DISTORTION (dBc) 60 2ND HARMONIC DISTORTION (dBc) MAX3503 toc12 0.9 -20 OUTPUT NOISE (dBmV IN 160kHz) 0.8 TRANSMIT NOISE vs. GAIN CODE MAX3503 toc11 0.9 GAIN STEP (dB) 1.0 MAX3503 toc10 1.0 OUTPUT RETURN LOSS (dB) MAX3503 Upstream CATV Amplifier _______________________________________________________________________________________ Upstream CATV Amplifier OUTPUT SPECTRUM -10 -20 -20 -30 -30 -40 -40 -50 -50 -60 -60 -70 -70 -80 -80 100kHz/div VOUT = 61dBmV α = 0.25 1280ksps 0 (dB) (dB) -10 VOUT = 61dBmV α = 0.25 160ksps MAX3503 toc20 0 OUTPUT SPECTRUM 10 MAX3503 toc19 10 6MHz/div Pin Description PIN NAME DESCRIPTION 1 VCC Programmable-Gain Amplifier (PGA) 3.3V Supply. Bypass to GND with a 0.1µF decoupling capacitor as close to the part as possible. 2 IN+ Positive PGA Input. Along with IN-, this port forms a high-impedance differential input to the PGA. Driving this port differentially increases the rejection of second-order distortion at low output levels. 3 GND PGA RF Ground. As with all ground connections, maintain the shortest possible (low-inductance) length to the ground plane. 4 IN- 5 GND Ground 6 SDA Serial-Interface Data. TTL-compatible input. See Serial Interface section. 7 SCLK Serial-Interface Clock. TTL-compatible input. See Serial Interface section. 8 CS Serial-Interface Enable. TTL-compatible input. See Serial Interface section. 9 TXEN Transmit Enable. Drive TXEN high to place the device in transmit-enable mode. 10 SHDN Shutdown. When SHDN is set low, all functions (including the serial interface) are disabled. 11,13,17–20 N.C. No Connection 12 OUT- Negative Output. Along with OUT+, this port forms a 75Ω impedance output. This port is matched to a 75Ω load using a 1:1 transformer. 14 OUT+ Negative PGA Input. When not used, this port must be AC-coupled to ground. See IN+. Positive Output. See OUT-. Output Amplifier Bias, 3.3V Supply. Bypass to GND with a 0.1µF decoupling capacitor as close to the part as possible. 15 VCC 16 CEXT RF Output Bypass. Bypass to GND with a 0.1µF capacitor. Exposed Paddle GND Ground _______________________________________________________________________________________ 7 MAX3503 Typical Operating Characteristics (continued) (Typical Application Circuit, VCC = 3.3V, VIN = 34dBmV, TXEN = SHDN = high, fIN = 20MHz, ZLOAD = 75Ω, TA = +25°C, unless otherwise noted.) Upstream CATV Amplifier MAX3503 Functional Diagram TXEN SHDN VCC BIAS CONTROL MAX3503 HIGH POWER OUTCEXT IN+ OUT+ INLOW NOISE D/A CONVERTER SERIAL DATA INTERFACE CS SDA SCLK GND Detailed Description Programmable-Gain Amplifier The PGA consists of the variable-gain amplifier (VGA) and the digital-to-analog converter (DAC), which provide better than 56dB of output-level control in 0.5dB steps. The PGA is implemented as a programmable Gilbert-cell attenuator. The gain of the PGA is determined by a 7-bit word (D6–D0) programmed through the serial data interface (Tables 1 and 2). Specified performance is achieved when the input is driven differentially. The device may be driven single ended. To drive the device in this manner, one of the input pins must be capacitively coupled to ground. Use a capacitor value large enough to allow for a lowimpedance path to ground at the lowest frequency of operation. For operation down to 5MHz, a 0.001µF capacitor is recommended. Output Amplifiers The output amplifiers are Class A differential amplifiers, capable of driving 61dBmV (QPSK) differentially. This architecture provides superior even-order distortion performance but requires that a transformer be used to convert to a single-ended output. In transmit-disable 8 mode, the output amplifiers are powered down. A resistor is placed across the output, so that the output impedance remains matched when the amplifier is in transmit-disable mode. Disabling the output devices also results in low output noise. To match the output impedance to a 75Ω load, the transformer must have a turns ratio of 1:1. The differential amplifier is biased directly from the 3.3V supply using the center tap of the output transformer. This provides a significant benefit when switching between transmit mode and transmit-disable mode. Stored energy due to bias currents cancels within the transformer and prevents switching transients from reaching the load. Serial Interface The serial interface has an active-low enable (CS) to bracket the data, with data clocked in MSB first on the rising edge of SCLK. Data is stored in the storage latch on the rising edge of CS. The serial interface controls the state of the PGA and the output amplifiers. Tables 1 and 2 show the register format. Serial-interface timing is shown in Figure 1. _______________________________________________________________________________________ Upstream CATV Amplifier The MAX3503 has two transmit modes, high power (HP) and low noise (LN). Each of these modes is actuated by the high-order bit, D7, of the 8-bit programming word. When D7 is a logic 1, HP mode is enabled. When D7 is a logic 0, LN mode is enabled. Each of these modes is characterized by the activation of a distinct output stage. In HP mode, the output stage exhibits 10.5dB higher gain than LN mode. The lower gain of LN output stage allows for significantly lower output noise and lower transmit-enable/transmit-disable transients. The full range of gain codes (D6–D0) can be used in either mode. For DOCSIS applications, HP mode is recommended for output levels at or above 10.5dBmV (D7 = 1, gain code = 83), LN mode when the output level is below 9.5dBmV (D7 = 0, gain code = 112). Shutdown Mode In normal operation, the shutdown pin (SHDN) is held high. When SHDN is taken low, all circuits within the IC are disabled. Only leakage currents flow in this state. Data stored within the serial-data interface latches are lost upon entering this mode. Current consumption is reduced to 5µA (typ) in shutdown mode. G A High-Power and Low-Noise Modes D7 D6 C B D5 A. tSENS B. tSDAS C. tSDAH D. tSCKL D4 D3 D D2 E D1 MAX3503 Applications Information F D0 E. tSCKH F. tSENH G. tDATAH/tDATAL Figure 1. Serial-Interface Timing Diagram Table 1. Serial-Interface Control Word BIT MNEMONIC DESCRIPTION MSB 7 D7 High-power/low-noise mode select 6 D6 Gain code, bit 6 5 D5 Gain code, bit 5 Transformer 4 D4 Gain code, bit 4 To match the output of the MAX3503 to a 75Ω load, a 1:1 transformer is required. This transformer must have adequate bandwidth to cover the intended application. Note that most RF transformers specify bandwidth with a 50Ω source on the primary and a matching resistance on the secondary winding. Operating in a 75Ω system tends to shift the low-frequency edge of the transformer bandwidth specification up by a factor of 1.5, because of primary inductance. Keep this in mind when specifying a transformer. Bias to the output stage is provided through the center tap on the transformer primary. This greatly diminishes the on/off transients present at the output when switching between transmit and transmit-disable modes. Commercially available transformers typically have adequate balance between half-windings to achieve substantial transient cancellation. Finally, keep in mind that transformer core inductance varies proportionally with temperature. If the application requires low temperature extremes (less than 0°C), adequate primary inductance must be present to sustain low-frequency output capability as temperatures drop. In general this is not a problem, as modern RF transformers have adequate bandwidth. 3 D3 Gain code, bit 3 2 D2 Gain code, bit 2 1 D1 Gain code, bit 1 LSB 0 D0 Gain code, bit 0 Input Circuit To achieve rated performance, drive the inputs of the MAX3503 differentially with an appropriate input level. The differential input impedance is approximately 2kΩ. Most applications requires a differential lowpass filter preceding the device. The filter design dictates a terminating impedance of a specified value. Place this load impedance across the AC-coupled input pins (see the Typical Operating Circuit). The MAX3503 has sufficient gain to produce an output level of 61dBmV (QPSK) when driven with a 34dBmV input signal. When a lower input level is present, the maximum output level is reduced proportionally and output linearity increases. If an input level greater than 34dBmV is used, the 3rd-order distortion performance degrades slightly. If single-ended sources drive the MAX3503, one of the input terminals must be capacitively coupled to ground _______________________________________________________________________________________ 9 MAX3503 Upstream CATV Amplifier Table 2. Chip-State Control Bits GAIN CODE (DECIMAL) SHDN TXEN D7 D6 D5 D4 D3 D2 D1 D0 0 X X X X X X X X X Shutdown mode 1 0 X X X X X X X X Transmit-disable mode 1 1 1 X X X X X X X Transmit-enable mode, high power 1 1 0 X X X X X X X 1 1 0 0 1 1 0 0 0 0 43 AV = -26.0dB* 1 1 0 1 0 1 0 0 0 0 92 AV = -0.5dB* AV = -95dB* STATES Transmit-enable mode, low noise 1 1 0 1 1 0 1 1 1 0 112 1 1 1 1 0 1 0 1 1 0 83 AV = -10.5dB* 1 1 1 1 1 0 1 1 1 1 99 AV = -18.5dB* 1 119 AV = -28.5dB* 1 1 1 1 1 1 0 1 1 *Typical gain at +25°C, VCC = 3.3V. (IN+ or IN-). The value of this capacitor must be large enough to look like a short circuit at the lowest frequency of interest. For operation at 5MHz with a 75Ω source impedance, a value of 0.001µF suffices. Layout Issues A well-designed PC board is an essential part of an RF circuit. For best performance, pay attention to power-supply layout issues as well as to the output circuit layout. Output Circuit Layout The differential implementation of the MAX3503’s output has the benefit of significantly reducing even-order distortion, the most significant of which is 2nd harmonic distortion. The degree of distortion cancellation depends on the amplitude and phase balance of the overall circuit. Keep the trace lengths from the output pins equal. Power-Supply Layout For minimal coupling between different sections of the IC, the ideal power-supply layout is a star configuration. This configuration has a large-value decoupling capacitor at the central power-supply node. The powersupply traces branch out from this node, each going to 10 a separate power-supply node in the circuit. At the end of each of these traces is a decoupling capacitor that provides very low impedance at the frequency of interest. This arrangement provides local power-supply decoupling at each power-supply pin. The power-supply traces must be made as thick as is practical. Ground inductance degrades distortion performance. Therefore, make ground plane connections with multiple vias. Exposed-Paddle Thermal Considerations The MAX3503’s 20-pin QFN package provides a low thermal-resistance path to the die. The PC board on which the MAX3503 is mounted must be designed to conduct heat from this contact. In addition, the EP should be provided with a low-inductance path to electrical ground. Maxim recommends that the EP be soldered to a ground plane on the PC board, either directly or through an array of plated via holes. Chip Information TRANSISTOR COUNT: 1180 SUBSTRATE CONNECTED TO GND ______________________________________________________________________________________ Upstream CATV Amplifier 10 CONTROL LOGIC SHDN GND TXEN VCC 9 N.C. 0.1µF 3.3V 15 0.001µF 2 + INPUT IN+ OUT+ ANTI-ALIAS FILTER MAX3503 3.3V 0.1µF OUTPUT 3.3V 4 - 1:1 14 0.001µF 1 3 OUT- 12 0.1µF IN0.1µF VCC CEXT GND N.C. GND 16 5 7 SCLK N.C. N.C. SDA CS 6 8 CONTROL LOGIC ______________________________________________________________________________________ 11 MAX3503 Typical Application Circuit Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 32L QFN .EPS MAX3503 Upstream CATV Amplifier 12 ______________________________________________________________________________________ Upstream CATV Amplifier 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. MAX3503 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)