900MHz ISM-Band, 250mW Power Amplifiers with Analog or Digital Gain Control

Transcription

1 9-47; Rev ; 6/ 9MHz ISM-Band, 2mW Power Amplifiers General Description The /MAX22 low-voltage, silicon RF power amplifiers (PAs) are designed for use in the 9MHz ISM band. They operate from a single +2.7 to +. supply, allowing them to be powered directly from a - cell NiCd or a -cell Lithium-Ion battery. The devices typically deliver 2mW (+24dBm) of output power at 9MHz from a single +.6 supply, or mw (+22dBm) from a single +2.7 supply. At +24dBm output power, power-added efficiency (PAE) is 44%. The /MAX22 provide 24dB of gain, which is adjustable over a continuous 24dB span via the analog gain-control pin of the or in two db steps via the 2-bit programmable gain-control DAC of the MAX22. An external capacitor sets the RF output power envelope ramp time, reducing spurious emissions during power-up and power-down by providing a gradual change in output power (). The /MAX22 feature a low-power shutdown mode, which typically draws less than µa of supply current, saving power during idle slots in time-division multiple-access (TDMA) systems. The SWR of the RF input in shutdown mode relative to normal operation is.2:. The devices also feature a thermal shutdown function, enabling the PA to protect itself from excessive temperature conditions that could damage the IC. A capacitor to ground limits thermal cycling by setting a thermal shutdown timeout period. The /MAX22 are available in a space-saving, thermally enhanced 6-pin power-qsop (PQSOP) package. 9MHz ISM Band Digital Cordless Phones Wireless Data FM Analog Transmitters 6MHz European ISM Band Applications Features MHz to MHz Frequency Range 2mW (+24dBm) Output Power at 9MHz from +.6 Supply +2.7 to +. Single-Supply Operation 44% Power-Added Efficiency 24dB Power Gain 24dB Analog Gain-Control Range () Three Levels of Digitally Programmed Power Gain in db Steps (MAX22) Programmable RF Power Envelope Ramping () Thermal Shutdown Programmable Thermal Shutdown Timeout Period.2µA Low-Power Shutdown Mode Low WSR in Standby and Shutdown Modes PART EEE MAX22EEE TOP IEW SHDN (D) CTRL (D) 2 4 Ordering Information TEMP. RANGE -4 C to + C -4 C to + C MAX22 6 PIN-PACKAGE 6 PQSOP 6 PQSOP Pin Configuration 4 RAMP+ (N.C.) RAMP- (N.C.) 2 /MAX Functional Diagrams appear at end of data sheet. 9 N.C. PQSOP GROUND OF OUTPUT STAGE CONNECTED TO PACKAGE SLUG. ( ) ARE FOR MAX22. Maxim Integrated Products For price, delivery, and to place orders, please contact Maxim Distribution at , or visit Maxim s website at

2 9MHz ISM-Band, 2mW Power Amplifiers /MAX22 ABSOLUTE MAXIMUM RATINGS to...-. to +6. SHDN, CTRL, D, D to...-. to ( +.) I...mA Power (Ω AC-coupled source)....+dbm Output Load SWR....6: 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 Continuous Power Dissipation (T A = +7 C) 6-Pin PQSOP (derate mw/ C above +7 C)...W Operating Temperature Range...-4 C to + C Storage Temperature Range...-6 C to + C Lead Temperature (soldering, s)...+ C ( = +2.7 to +., CTRL = +2.2, SHDN = D = D = +2, T A = -4 C to + C. No input signal applied, unless otherwise noted. Typical values are at = +.6 and.) PARAMETER Supply oltage Range Shutdown Supply Current Standby Supply Current Logic Input High Logic Input Low CTRL Input for Standby Mode CTRL Input for Gain-Control Mode SYMBOL I CC I CC IH IL CTRL CTRL SHDN =.6,.6 D = D =.6 =. CTRL.4 () SHDN (), D, D (MAX22) SHDN (), D, D (MAX22) CONDITIONS MIN TYP MAX UNITS µa ma Logic Input Current CTRL Input Current I IH SHDN = 2. (), D = D = 2. (MAX22) - I IL SHDN = (), D = D = (MAX22) - µa CTRL = CTRL = µa AC ELECTRICAL CHARACTERISTICS (/MAX22 Evaluation Kit, = +.6, CTRL = +2.2, SHDN = (), D = D = (MAX22), P = dbm, ƒ = 9MHz,, unless otherwise noted.) Frequency Range Power Gain Output Power PARAMETER Output Power ariation Over Temperature SYMBOL ƒ IN G P P OUT P OUT (Notes, 2) = 4. =.6 (Note ) =. = 2.7 CONDITIONS T A = T MIN to T MAX (Note ) MIN TYP MAX UNITS MHz db dbm db Output Power, Medium-Power Mode P OUT D =, D = (MAX22 only). dbm 2

3 9MHz ISM-Band, 2mW Power Amplifiers AC ELECTRICAL CHARACTERISTICS (continued) (/MAX22 Evaluation Kit, = +.6, CTRL = +2.2, SHDN = (), D = D = (MAX22), P = dbm, ƒ = 9MHz,, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Output Power, Low-Power Mode P OUT D =, D = (MAX22 only) 6. dbm Gain-Control Range (Note ) G P.6 < CTRL < 2.2 ( only) 2.6 db Power-Added Efficiency PAE 44 % Power-Added Efficiency at +2dBm Output Power Supply Current, Medium-Power Mode Supply Current, Low-Power Mode Input SWR Input SWR Change, Shutdown Mode (Notes, 4) PAE I CC I CC SWR SWR CTRL adjusted to give P = +2dBm ( only) D =, D = (MAX22 only) D =, D = (MAX22 only) Z SOURCE = Ω (Note ) :.4: % ma ma /MAX22 Input SWR Change, Standby Mode (Notes, 4) SWR only.2: Off-Isolation SHDN = D = D = CTRL = ( only) 2 db Maximum Nonharmonic Spurious Output Due to Load Mismatch = +2.7 to +., 6: SWR at any phase angle, P = +dbm -6 dbc Maximum Output Load SWR Without Damage (Note) Any load phase angle, P = +dbm, T A = T MIN to T MAX 6: Harmonic Suppression (Note ) 29 dbc Autoramping Rise Time C RAMP =.22µF (Notes, 6) ( only).9 ms Autoramping Fall Time C RAMP =.22µF (Notes, 7) ( only).2 ms Output Power Rise Time RAMP+ = RAMP- = unconnected (Note 6).4 µs Thermal Shutdown Temperature T TH P = dbm, = C Thermal Shutdown Timeout Period t TH C =.22µF (Note ) 9 ms Note : Guaranteed by design. Note 2: Operation outside this range is possible, but not characterized. Note : Gain is monotonic with CTRL. Note 4: Input SWR relative to input impedance in operating mode. Note : Harmonics measured on evaluation kit, which provides some harmonic attenuation in addition to the rejection provided by the IC. The combined suppression is specified. Note 6: Time measured from SHDN () low-to-high transition to when output power is within db of final value. Includes effects of % tolerance capacitor. Note 7: Time measured from SHDN () high-to-low transition to when output power is -2dB of final value. Includes effects of % tolerance capacitors. Note : Time from die temperature dropping below Thermal Shutdown Temperature, T TH, to when the device turns itself back on.

4 9MHz ISM-Band, 2mW Power Amplifiers /MAX22 Typical Operating Characteristics (/MAX22 Evaluation Kit, = +.6, CTRL =, SHDN = D = D =, P = dbm, f = 9MHz,, unless otherwise noted.) SHUTDOWN SUPPLY CURRENT (µa)... SHUTDOWN SUPPLY CURRENT vs. SUPPLY OLTAGE T A = -4 C SUPPLY OLTAGE () / toc SUPPLY CURRENT (ma) 2 2 STANDBY SUPPLY CURRENT vs. SUPPLY OLTAGE SHDN = CTRL = = UNCONNECTED T A = -4 C SUPPLY OLTAGE () / toc2 OUTPUT POWER (dbm) OUTPUT POWER vs. SUPPLY OLTAGE T A = -4 C SUPPLY OLTAGE () / toc POWER-ADDED EFFICIENCY (%) POWER-ADDED EFFICIENCY vs. SUPPLY OLTAGE T A = -4 C / toc4 OUTPUT POWER (dbm) 2 2 OUTPUT POWER vs. FREQUENCY MAX22 (D = D = ), AND MAX22 (D =, D = ) MAX22 (D =, D = ) / toc OUTPUT POWER (dbm) OUTPUT POWER vs. GAIN CONTROL OLTAGE 2 2 T A = -4 C / toc SUPPLY OLTAGE () FREQUENCY (MHz) CTRL () OUTPUT POWER AND POWER-ADDED EFFICIENCY vs. INPUT POWER / toc7 2 P T A = -4 C OUT OUTPUT POWER (dbm) 2 T A = -4 C PAE INPUT POWER (dbm) PAE (%) SWR PORT SWR vs. FREQUENCY SHUTDOWN MODE STANDBY MODE NORMAL OPERATION FREQUENCY (MHz) LINEAR SCALE OUTPUT POWER vs. SHUTDOWN CONTROL / toc C RAMP =.22µF 4 / toc ms/div SHUTDOWN OUTPUT POWER

5 9MHz ISM-Band, 2mW Power Amplifiers PIN MAX22 FUNCTION Open-Collector, RF Output Port. Connect output matching network to this pin. 9 9,, 4 N.C. No Connection. Do not make a connection to this pin. Second Stage Supply oltage. Bypass with appropriate capacitors to. 2 2 Input Stage Supply oltage. Bypass with appropriate capacitors to. 4 NAME RF Input Port. Requires external matching network and blocking capacitor , 6, SHDN D CTRL D RAMP- RAMP+ Pin Description Input Stage Ground. Connect directly to low-inductance ground plane. If vias are used, separate them from other pin vias. Shutdown Control Input. Drive SHDN low to place the device in shutdown mode. Drive high for normal operation. Digital Gain/Shutdown Control Input. MSB of the 2-bit digital output power control. D and D set the output power to one of three discrete levels. To place the device in shutdown, drive D and D low (Table 2). Analog Gain-Control Input. Apply a voltage between.6 and 2.2 to vary the gain of the PA. Drive CTRL below.4 to place the device in standby mode. Drive CTRL above 2.2 to place the device in peak output power mode. Digital Gain/Shutdown Control Input. LSB of the 2-bit digital output power control. D and D set the output power to one of three discrete levels. To place the device in shutdown, drive D and D low (Table 2). Second Stage Ground. Connect directly to low-inductance ground plane. If vias are used, separate them from other pin vias. Output Stage Ground. Connect directly to low-inductance ground plane. If vias are used, separate them from other pin vias. Thermal Shutdown Timeout Capacitor Terminal. Connect a capacitor from to ground to limit thermal cycling. Negative Terminal of Output Power Ramp Capacitor. Connect capacitor, C RAMP, between RAMP+ and RAMP- to control the rise and fall time of the output power ramp. Positive Terminal of Output Power Ramp Capacitor. Connect capacitor, C RAMP, between RAMP+ and RAMP- to control the rise and fall time of the output power ramp. Bias Circuitry Ground. Connect directly to low-inductance ground plane. If vias are used, separate them from other pin vias. 6 6 Bias Circuitry Supply oltage. Bypass with appropriate capacitors to. SLUG SLUG Output Stage Ground. Provides additional thermal conduction, as well as a low-inductance path to ground. Connect directly to low-inductance ground plane. /MAX22

6 9MHz ISM-Band, 2mW Power Amplifiers /MAX22 Detailed Description The /MAX22 are nonlinear power amplifiers (PAs) intended for constant envelope applications (FM, FSK, GMSK). The devices operate over the 92MHz to 92MHz frequency range and provide typically 2mW of output power and 44% efficiency from a single +2.7 to +. supply. Both devices typically provide 24dB of gain, which is adjustable over a continuous 24dB range through an analog voltage on CTRL of the or in two db steps through the 2-bit programmable gain inputs (D, D) on the MAX22. A low-power shutdown mode on both devices reduces supply current to.2µa. All bias, gain control, and temperature-sensing circuitry is provided on-chip to save board space and reduce component count. The signal path includes a variable gain amplifier (GA), an output driver, and an output power transistor. On-chip interstage matching networks are provided for optimal loading and power transfer. Internal bias circuitry responds to CTRL and SHDN of the, or to the 2-bit gain/shutdown control DAC of the MAX22, providing optimum biasing and efficiency as well as shutdown and ramp control functions. A unique temperature-sensing circuit protects the device from overheating by shutting down the PA until a safe temperature is resumed. The devices come in a 6-pin PQSOP package, which incorporates a slug on the bottom of the device to increase heat conduction and provide a low inductance path to ground. RF Input Stage (ariable Gain Amplifier) The input stage includes a variable gain amplifier (GA) with 24dB gain-control range. With the appropriate matching network, the input SWR is nominally.: during operation and the change in SWR is only.2:, relative to normal operation. This stage remains active during standby mode () to provide a constant input impedance but is off during shutdown mode (/MAX22). AC-couple this port with a DC-blocking capacitor. RF Second Stage (Driver) The driver provides gain to overcome interstage matching losses and to produce a signal large enough to drive the output power transistor into saturation. The driver stage is off during standby () and shutdown (/MAX22) modes. RF Output Stage (Output Power Transistor) The output power transistor delivers +24dBm of output power from a single +.6 supply. The transistor s open-collector output requires a pull-up inductor to for proper biasing, as well as a proper output matching network to ensure optimum output power. Connect the output matching network to (pin ). See the Typical Application Circuit for bias and matching components suitable for 9MHz operation. The ground of the output stage is connected to a metal slug on the bottom of the /MAX22 s 6-pin PQSOP package. The metal slug increases heat conduction and provides a low-inductance path to ground. Solder the metal slug to the PC-board ground plane. Analog Gain Control and Power Management Shutdown Mode Drive the shutdown (SHDN) pin below.6 to place the in shutdown mode. The GA, driver, and output transistor are off in shutdown mode and the supply current is typically reduced to.2µa. When SHDN is above 2., the device is enabled. Standby Mode Drive SHDN above 2. and CTRL below.4 to place the in standby mode. In standby mode, the GA remains biased while the driver and output transistor are disabled. Supply current is typically 2mA in standby mode. This mode allows the device to maintain a good input SWR while maintaining db of isolation. This is useful to users who drive the PA with a direct modulated CO, where pulling of the CO results from changes in the input SWR. Analog Gain Control The voltage applied to the gain-control (CTRL) pin varies the output power of the continuously over a 24dB range. An internal comparator holds the PA to a constant peak output power if CTRL is above 2.2. For CTRL below.4, the PA is in standby mode. CTRL presents a high input impedance, allowing the CTRL voltage to be set with a resistor-divider or a voltage output DAC. Output Power Autoramping The internal bias circuitry of the automatically ramps the output power of the PA down or up at a constant rate (in W/sec) when switched in or out of shutdown mode. The output power is ramped to the level set by CTRL on the. The output power rise and fall time ramp is set by placing a capacitor, C RAMP, between RAMP+ and RAMP-. This provides an easy means of avoiding spectral splatter and complying with transmit mask requirements, without using a separate controller. The output power rise and fall time is set by the value of C RAMP. 6

7 9MHz ISM-Band, 2mW Power Amplifiers MAX22 Digital Gain Control and Power Management The MAX22 responds to logic-level signals at the device s 2-bit DAC inputs, D and D, placing the device in shutdown mode or into one of three discrete output power levels. See Table 2 for operating modes and output power levels. Setting D and D to a logiclevel low places the device in shutdown mode and reduces supply current to.2µa. The GA, driver, and output stage are off in shutdown mode, while the input impedance is only slightly changed. Setting D and D to one of the other three modes adjusts the output power to one of three discrete levels in db steps. Thermal Shutdown The /MAX22 feature a thermal shutdown mode that helps to protect the device from damage when the die temperature becomes excessive. If the temperature of the die exceeds the thermal shutdown temperature, T TH, the GA is forced into a low-gain mode and output power is reduced to a minimum. After Table. Operating Modes MODE Shutdown SHDN <.6 Standby > 2. ariable Gain > 2. CTRL X.4.6 CTRL < 2.2 OUTPUT POWER (P = dbm, = +.6) < -dbm < -dbm dbm to +24dBm Maximum Gain > 2. > dbm X = Don t care the PA s die temperature drops below T TH, the device remains in thermal shutdown mode for the thermal shutdown timeout period, t TH. A single capacitor, C, from to ground sets t TH. The thermal shutdown timeout period helps to limit device thermal cycling that results if the source of the excessive temperature is not removed. t TH is set by the value of C. Applications Information Proper attention to voltage supply bypassing is essential for high-frequency RF circuit stability. Bypass with.µf, nf, and pf capacitors in parallel with each other to ground. Use separate vias to the ground plane for each of the bypass capacitors and minimize trace length to reduce inductance. Use separate vias to the ground plane for each ground pin. Use low-inductance ground connections. Decouple SHDN, CTRL, D, and D with.µf capacitors to ground to minimize noise on the internal bias cell. Use a series resistor (typically Ω) to further reduce coupling of high-frequency signals into the control pins. Table 2. MAX22 Operating Modes Truth Table MODE D Shutdown Low Power < -dbm +6.dBm Medium Power +dbm High Power +24dBm D OUTPUT POWER (P = dbm, = +.6) Functional Diagrams /MAX22 RAMP+ RAMP- SHDN CTRL BIAS TEMP SENSOR D D BIT DAC 6 BIAS MAX22 TEMP SENSOR GA DRIER GA DRIER 2, 6 7, SLUG 2, 6 7, SLUG 7

8 9MHz ISM-Band, 2mW Power Amplifiers /MAX22.22µF.22µF nh 6pF pf pf 2.nH.6pF SHDN (D) CTRL (D) 27nH MAX22 RAMP+ (N.C.) RAMP- (N.C.) N.C Typical Application Circuit C RAMP.22µF pf pf pf nf nf C.22µF nf.µf.µf.µf NOTES: ( ) APPLIES TO MAX22. BACKSIDE SLUG MUST BE SOLDERED TO GROUNDPLANE. pf nf.µf Package Information PSSOPPS.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, 2 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.