Ordering number : EN5689A Monolithic Linear IC LA7790M QPSK Transmitter for Cable TV Overview The LA7790M is a QPSK data transmitter for digital cable TV applications. By integrating the I/Q quadrature modulator, RF amplifier, electronic volume control, mute control, and other functions onto a single chip, parts count is reduced and set size is miniaturized. Features • Maximum RF amplifier output level of +10 dBm (75Ω terminator), suitable for directly driving the cable. • RF output frequency range of 5 to 70 MHz. Frequency range selection function permits broadband designs. • Electronic volume control for direct-current control of RF output level. • Muting ensures ample attenuation during periods with no transmission. • Support for both internal and external bias for I/Q modulation inputs. • Support for I/Q modulation frequencies up to 10 MHz. (typ: 500 mVp-p) • • • • • • Varactor diode-based VCO Muting Electronic volume control Power-saving modes Switchable output frequency range Power supply voltage of 5 V (4.5 to 5.5 V) Package Dimensions unit: mm 3108-MFP24D [LA7790M] Functions • I/Q quadrature modulator • I/Q input bias power supply • RF amplifier Allowable power dissipation, Pdmax (mW) SANYO: MFP24D Ambient temperature, Ta (°C) SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110 JAPAN 5061998RM (OT) No. 5689-1/14 LA7790M Specifications Maximum Ratings at Ta = 25°C Parameter Maximum power supply voltage Circuit voltage Symbol VCC max Vmax I11 Circuit current I19 Allowable power dissipation Pd max Conditions Ratings Pins 1, 10, and 24 Pins 1, 12, 17, 20, 21, and 23 V VCC V 1 mA 2 mA 650 mW Output lead-in current Ta ≤ 54°C Unit 7 Operating ambient temperature Topr –20 to +70 °C Storage temperature Tstg –55 to +150 °C Ratings Unit Recommended Conditions at Ta = 25°C Parameter Operating power supply voltage Symbol VCC op Conditions Pins 1, 10, and 24 4.5 to 5.5 V Operating Characteristics at Ta = 25°C, VCC = 5.0 V Parameter Symbol Conditions Ratings min typ Unit max Current drain Circuit current 1 I1 Circuit current 2 I24 + I10 With no signal, pin 1 26 33 44 mA With no signal, pins 24 and 10 44 55 73 mA 70 MHz –2 dBm Modulator fo: f(V19) = 25 MHz Output frequency range f(V19) 5 V19(DSB) Note 1: V20 = V23 = GND, V12 = V17 = V21 = VCC, S1 = A –7 V19(HD2) Note 2: V20 = V23 = GND, 40 dB V19(HD3) V12 = V17 = V21 = VCC, S1 = A 35 dB Output secondary harmonic distortion V19(2fo) Note 3: V20 = V23 = GND, V12 = V17 = V21 = VCC, S1 = A 20 dB Output tertiary harmonic distortion V19(3fo) Note 3: V20 = V23 = GND, V12 = V17 = V21 = VCC, S1 = A 8 dB Carrier suppression ratio V19(fo) Note 4: V20 = V23 = GND, V12 = V17 = V21 = VCC, S1 = A 30 dB V19(SSB) Note 5: V20 = V23 = GND, V12 = V17 = V21 = VCC, S1 = A 30 dB Output signal level Output harmonic distortion Sideband suppression ratio –4 I input level V4.5 V4.5 = |V4 — V5| 500 Q input level V8.9 V8.9 = |V8 — V9| 500 I input DC voltage V4, 5 External DC bias voltage 1.9 2.1 2.3 V Q input DC voltage V8, 9 External DC bias voltage 1.9 2.1 2.3 V Reference voltage V6 Internal DC bias voltage 1.9 2.1 2.3 V V21 V12 = V17 = VCC, V20 = V23 = GND, S1 = A 0 0.5 V V19(GR) Note 6: V20 = V23 = GND, V12 = V17 = VCC, S1 = A, V21 = VCC → 0.5 V 45 R19 V12 = V17 = V21 = VCC, V20 = V23 = GND, S1 = A 80 f(osc) V12 = V17 = V21 = VCC, V20 = V23 = GND, S1 = A 20 V11(fo) V12 = V17 = V21 = VCC, V20 = V23 = GND, S1 = A 500 R11 V12 = V17 = V21 = VCC, V20 = V23 = GND, S1 = A 200 Band switch 1 “H” level f(V19) = 25 MHz V17H Note 7: V12 = V21 = VCC, V20 = V23 = GND, S1 = A 4 Band switch 1 “L” level f(V19) = 12.5 MHz V17L Note 7: V12 = V21 = VCC, V20 = V23 = GND, S1 = A mVp-p mVp-p Variable attenuator Minimum gain control voltage Gain range Modulator output impedance dB 160 Ω 280 MHz 700 900 mVp-p 300 400 Ω 120 VCO Oscillator frequency range VCO output level VCO output impedance Band switch V 1 V Continued on next page. No. 5689-2/14 LA7790M Continued from preceding page. Parameter Symbol Conditions Band switch 2 “H” level f(V11) = 25 MHz V12H Note 7: V17 = V21 = VCC, V20 = V23 = GND, S1 = A Band switch 2 “L” level f(V11) = 12.5 MHz V12L Note 7: V17 = V21 = VCC, V20 = V23 = GND, S1 = A Ratings min typ Unit max 4 V 1 V 13 dBm RF output amplifier Maximum output level Maximum output distortion V1 max V1(HD2) V1(HD3) Note 8: V12 = V17 = V21 = VCC, V20 = V23 = GND, SG3 = –6 dBm, S1 = A Note 8: V12 = V17 = V21 = VCC, V20 = V23 = GND, SG3 = –6 dBm, S1 = A 7 10 40 dBc 40 dBc 4 V Muting Muting on voltage V23H V12 = V17 = V21 = VCC, V20 = GND, S1 = B Muting off voltage V23L V12 = V17 = V21 = VCC, V20 = GND, S1 = B Muting attenuation V1(mute) Note 9: V23 = 1 V → 4 V V12 = V17 = V21 = VCC, V20 = GND, S1 = B 1 70 V dB Power save function Power save on voltage V20H Power save off voltage V20L Power save current I1 4 V 1 Note 10: V20 = 4 V 0 0.1 V mA Pin Assignment No. 5689-3/14 LA7790M Note 1 Input: SG1 =1 MHz CW, 500 mVp-p, SG2 = No Signal or SG2 = 1 MHz CW, 500 mVp-p, SG1 = No Signal Output: Note 2 Input: Same as Note 1 Output: Note 3 Input: Same as Note 1 Output: Note 4 Input: SG1 = SG2 = 1 MHz CW, 500 mVp-p Output: Note 5 Input: SG1 = 1 MHz CW, 500 mVp-p, 0deg SG1 = 1 MHz CW, 500 mVp-p, 90deg Output: Note 6 Input: SG1 = 1 MHz CW, 500 mVp-p Output: No. 5689-4/14 LA7790M Note 7 Input: SG1 = 1 MHz CW, 500 mVp-p Output: Note 8 Input: SG3 = 25 MHz CW, –6 dBm Output: Note 9 Input: SG1 = 1 MHz CW, 500 mVp-p Output: Note 10 I1 = pin 1 current when V20 = 4 V (power save on). No. 5689-5/14 Mute Gain control Voltage reference Divider Power save Band switch 1 Divider Band switch2 LA7790M Measurement Circuit No. 5689-6/14 Mute Gain control Voltage reference Divider Power save Band switch 1 Divider Band switch2 LA7790M Sample Application Circuit No. 5689-7/14 LA7790M 1. Modulator The modulator consists of two identical multiplier circuits, creating I and Q channels. Pins 4 & 5 and pins 8 & 9 are I and Q channel inputs, respectively. These pins must be biased at 2.1 ± 0.2 V. Pin 6 is an internal 2.1 V bias. This internal bias can be used if the I & Q data inputs are AC coupled, but an external bias must be used in the case of DC coupled data inputs. Carrier suppression is improved if the offset voltages between pins 4 & 5 and pins 8 & 9 are small. (1) AC coupled application 4 + I input 5 6 2.1 V 8 Q input + 9 (2) DC coupled application + I input 2.1 V + 4 5 6 + Q input 2.1 V + 8 9 No. 5689-8/14 LA7790M Equivalent circuit of modulator block VCC 300 300 to HPF from Divider bias from Divider 2.1 V 1k 400 300 1.4 mA 4 I-INPUT 300 400 300 1.4 mA 1.4 mA 5 6 8 300 1.4 mA 9 Q-INPUT Unit (resistance : Ω) No. 5689-9/14 LA7790M 2. Attenuator The attenuator input signal comes from the modulator output via a high pass filter (fC = 2 MHz). The modulator output is pin 19. Pin 19 is connected to the emitter of an NPN emitter follower through a 100 Ω resistor. The emitter sink current is about 1 mA, but can be increased by the addition of an external resistor between pin 19 and ground. The minimum value for the external resistor is 1.5 kΩ. The output level of pin 19 can be adjusted using pin 21. Pin 21 is connected to the base of a PNP emitter follower through a 300 Ω resistor. When pin 21 = 0 V, the base current is about 10 µA. Equivalent circuit of attenuator block VCC 1k 1k Gain control 0 to 10 µA 300 21 Control Circuit 100 ATT 19 1k MOD output HPF 1 mA 1 mA 1 mA From Modulator Unit (resistance : Ω) 3. RF Amplifier The RF amplifier input signal comes from the attenuator output after the harmonics are removed by the LPF. The RF amplifier is composed of a two-stage amplifier and includes mute and power save functions. The gain of the RF amplifier can be adjusted using the external input resistor connected to pin 22 and the external load resistor connected to pin 1. The input of pin 22 must be AC coupled. The output of pin 1 must be connected to VCC via a choke coil. Pin 23 (mute control) and pin 20 (power save control) are both high impedance inputs (base current less than 10 µA). For normal operation, the voltage at pins 20 and 23 must be less than 1 V. For Mute and Power Save operation, the voltage at pins 20 are 23 must be between VCC–1 and VCC. No. 5689-10/14 LA7790M Equivalent circuit of RF amplifier block VCC Choke Coil Vout 0 to 3µA Mute 23 Load resistor 75 RF output 1 VCC 30 mA VCC 300 RF input 5k R2 300 from 1st stage Mute 2nd stage R1 22 Vin 1st stage 300 3.5 V 20 Power save 0 to 4 µA Power save R1 + R2 + 300 · ——————— RF Amplifier Gain = · R1 + 300 R1 : Input Resistor The gain of RF amplifier can be adjusted by changing the value R1. Unit (resistance : Ω) No. 5689-11/14 LA7790M 4. Oscillator The oscillator signal is divided by either 4 or 8, and supplied to the modulator as 0° and 90° switching signals. The division mode can be selected using Band Switch 1 (pin 17). Pin 17 = High → Modulation frequency = 1/4 oscillator frequency Pin 17 = Low → Modulation frequency = 1/8 oscillator frequency The oscillator requires an external coil and capacitors. Pins 14 & 15 should be DC coupled using a coil. A coil with Qu of 30 or greater is required and the impedance between pins 14 and 15 is 6 kΩ. The value of the coupling capacitors between pins 13 & 14 and pins 15 & 16 must be large enough so that the signal phase rotation is small. Equivalent circuit of oscillator block VCC 1k 1k 3k 3k 3.2 V 2.2 mA 13 14 15 16 Unit (resistance : Ω) No. 5689-12/14 LA7790M 5. Oscillator Output The output frequency of the oscillator is equal to or half of the output frequency of the modulator. The mode is set using Band Switch 2 (pin 12). Pin 12 = High → Oscillator output frequency = modulator frequency Pin 12 = Low → Oscillator output frequency = 1/2 modulator frequency 6. Band Swtich The input circuitry of Band Switch 1 (pin 17) and Band Switch 2 (pin 12) are the same. A low setting requires a voltage of less than 1 V at the pin. A high setting requires a voltage between VCC–1 and VCC at the pin. Settings of low or high generate currents of ±50 µA at pins 12 and 17. Pin 12, 17 = High → Sink current = 50 µA Pin 12, 17 = Low → Source current = 50 µA Equivalent circuit of osc output and band switch blocks VCC 20 k 20 k LPF from Divider from Divider 11 300 Band switch2 OSC OUTPUT 12 40 k 20 k 20 k 1 mA The input circuitry of band switch 1 is same. Unit (resistance : Ω) No. 5689-13/14 LA7790M 7. Digital ECL Circuit To get the correct 0°/90° phase switching signal for the modulator, a divide-by-four dual flip-flop is employed as shown in the following figure. Band Switch 1 can be usded to expand the range of the modulation frequency. Band Switch 2 can be used to select the frequency to output to an external PLL. OSC 1/2 L H 17 to Mudulator 90deg Q 0deg Q CL D Q D Q 1/2 12 11 Band switch2 H/L VCO output D CL D 1/2 L H Band switch H/L 1/2 1/2 1/2 ■ No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of which may directly or indirectly cause injury, death or property loss. ■ Anyone purchasing any products described or contained herein for an above-mentioned use shall: ➀ Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all damages, cost and expenses associated with such use: ➁ Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees jointly or severally. ■ Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied regarding its use or any infringements of intellectual property rights or other rights of third parties. This catalog provides information as of May, 1998. Specifications and information herein are subject to change without notice. PS No. 5689-14/14