MAX1474AXT-T ,Miniature Electronically Trimmable CapacitorApplicationsOrdering InformationPost-Trim of Low-Cost Regenerative ReceiversPIN- TOPPART TEMP. RANG ..
MAX1478AAE ,1% Accurate / Digitally Trimmed /Rail-to-Rail Sensor Signal ConditionerApplicationsTEMP 4 MAX1478 13 BDRIVEPiezoresistive Pressure and AccelerationFSOTC 5 12 INPTransduce ..
MAX1479ATE ,300MHz to 450MHz Low-Power, Crystal-Based +10dBm ASK/FSK TransmitterFeaturesThe MAX1479 crystal-referenced phase-locked-loop♦ ETSI-Compliant EN300 220(PLL) VHF/UHF tra ..
MAX1479ATE ,300MHz to 450MHz Low-Power, Crystal-Based +10dBm ASK/FSK TransmitterApplicationsPART TEMP RANGE PIN-PACKAGERemote Keyless EntryMAX1479ATE -40°C to +125°C 16 Thin QFN-E ..
MAX1479ATE+ ,300MHz to 450MHz Low-Power, Crystal-Based +10dBm ASK/FSK TransmitterApplicationsMAX1479ATE+ -40°C to +125°C 16 TQFN-EP*● Remote Keyless Entry+Denotes a lead(Pb)-free/R ..
MAX147BCAP ,+2.7Low-Power, 8-Channel, Serial 12-Bit ADCsApplications+3VPortable Data Logging Data AcquisitionVCH0 V DDDD 0.1μFMedical Instruments Battery- ..
MAX4053AESE+ ,Low-Voltage, CMOS Analog Multiplexers/SwitchesGeneral Description ________
MAX4053AESE+T ,Low-Voltage, CMOS Analog Multiplexers/SwitchesApplications♦ Low Distortion: < 0.04% (600Ω)Battery-Operated Equipment♦ Low Crosstalk: < -90dB (50Ω ..
MAX4053CEE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesELECTRICAL CHARACTERISTICS—Dual Supplies(V+ = +4.5V to +5.5V, V- = -4.5V to -5.5V, T = T to T , unl ..
MAX4053CEE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesELECTRICAL CHARACTERISTICS—Dual Supplies(V+ = +4.5V to +5.5V, V- = -4.5V to -5.5V, T = T to T , unl ..
MAX4053CSE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesGeneral Description ________
MAX4053CSE ,Low-Voltage / CMOS Analog Multiplexers/SwitchesFeaturesThe MAX4051/MAX4052/MAX4053 and MAX4051A/' Pin Compatible with Industry-Standard MAX4052A/M ..
MAX1474AXT-T
Miniature Electronically Trimmable Capacitor
General DescriptionThe MAX1474 is a fine-line (geometry) electronically trim-
mable capacitor (FLECAP) programmable through a
simple digital interface. There are 32 programmable
capacitance values ranging from 6.4pF to 13.3pF in
0.22pF increments (Table 1). The quartz dielectric
capacitance is highly stable and exhibits a very low volt-
age coefficient. It has virtually no dielectric absorption
and has a very low temperature drift coefficient
(<33ppm/°C). The MAX1474 is programmed through two
digital interface pins, which have Schmidt triggers and
pulldown resistors to secure capacitance programming.
CustomizationMaxim can customize the MAX1474 for specific high-
volume applications. Contact Maxim for further informa-
tion.
ApplicationsPost-Trim of Low-Cost Regenerative Receivers
Tunable RF Stages
Low-Cost, Low-Temperature Drift Oscillators
Garage Door Openers
Keyless Entry
Industrial Wireless Control
Capacitive Sensor Trimming
RFID Tags
FeaturesTiny SC70 Package (1.1mm x 2.2mm x 2.4mm) High-Performance Electronically Trimmable
CapacitanceVery Simple Digital InterfaceEliminates the Need for Mechanical TuningEnabling Technology for Low-Cost Production
Line AutomationFully Static Operation After Programming
(No Switching)
MAX1474
Miniature Electronically Trimmable Capacitor
Ordering Information19-1948; Rev 1; 3/01
Functional Diagram
Pin Configuration
MAX1474
Miniature Electronically Trimmable Capacitor
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICSStresses 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.
Note 1:Measurements made at CP with CM = GND.
Supply Voltage, VDDto VSS..................................... -0.3V to +6V
All Other Pins...................................(VSS- 0.3V) to (VDD+ 0.3V)
RMS Current into Any Pin....................................................50mA
Continuous Power Dissipation (TA= +70°C)
6-Pin SC70 (derate 3.1mW/°C above +70°C).............245mW
Operating Temperature Range
MAX1474AXT................................................-40°C to +125°C
Storage Temperature Range.............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s).................................+300°C
MAX1474
Miniature Electronically Trimmable CapacitorCAPACITANCE vs. TEMPERATURE
MAX1474 toc01
TEMPERATURE (°C)
S (pF)
CAPACITANCE vs. VOLTAGE
(SINGLE ENDED)
MAX1474 toc02
VOLTAGE (V)
(pF)
MAX1474 toc03
VOLTAGE (V)
(pF)
CAPACITANCE vs. VOLTAGE
(DIFFERENTIAL)3505006502008009501100
EFFECTIVE CAPACITANCE
vs. FREQUENCYMAX1474 toc04
FREQUENCY (MHz)
CAPACITANCE (pF)1001000
QUALITY FACTOR vs. FREQUENCYMAX1474 toc05
FREQUENCY (MHz)
QUALITY FACTOR vs. CAPACITANCE
MAX1474 toc06
CAPACITANCE (pF)
Typical Operating Characteristics(VDD= +5V, VSS= 0, TA= +25°C, unless otherwise noted.)
MAX1474
Detailed DescriptionThe MAX1474 consists of a binary-weighted array of
capacitors that can be switched in and out of parallel to
provide 32 monotonic steps. The switches implement-
ed allow the DC bias of either terminal of the capacitor
to be anywhere from ground to the supply voltage.
There is no inherent polarity. The signal swing range is
limited to 300mV above VDDand 300mV below VSS.
Therefore, if a large-signal swing range is desired, care
must be taken to bias the terminal(s) requiring high
swing capability near midsupply.
If the capacitance is measured differentially from one
terminal to the other, the greatest min/max ratio of the
binary array can be realized, allowing tuning from
0.42pF to 10.9pF in 0.34pF steps. If one terminal is
grounded, and the capacitance is measured to ground,
the parasitics inherent in the package will become
lumped with the switched array, allowing tuning from
6.4pF to 13.3pF in 0.22pF steps. When using the
MAX1474, it is recommended for optimal performance
to connect the CM terminal to the lowest impedance
node (i.e., ground or supply if possible) and CP to the
higher impedance node (i.e., the resonant node in a
ground-referenced LC tank circuit).
Digital InterfaceThe digital interface sets the desired capacitance
value. There are only two pins, EN and DAT, required
for this operation. EN is an active-high control signal.
Miniature Electronically Trimmable Capacitor
Typical Operating Characteristics (continued)(VDD= +5V, VSS= 0, TA= +25°C, unless otherwise noted.)
Pin Description
SMITH CHART:
31 DAT PULSESMAX1474 toc10
f1 = 848MHz
MAX1474
Miniature Electronically Trimmable CapacitorWhile EN is asserted, the internal counter counts posi-
tive edges of DAT. The number of sequential pulses on
DAT determines the capacitance setting. As EN is de-
asserted, the counter value is latched into the capaci-
tance control registers first, and then the counter is set
to zero. The programmed capacitance value then
appears between CP and CM. During the period when
EN is asserted, the capacitance value between CP and
CM stays unchanged. Figure 1 is a digital timing dia-
gram.
Q Enhancement CircuitSince the capacitors have the multiplexer series resis-
tance associated with them, the quality factor of the
trimmable capacitors is not high. For example, a 10pF
capacitor only has a theoretical Q of about 10 at
315MHz with 5Ωseries resistance. As in Figure 2, an
impedance transformer-like circuit is needed to over-
come this low Q. With this circuit, a much higher Q is
achievable using high-Q external capacitors. This con-
figuration allows a tuning range of approximately
314MHz to 319MHz with 160kHz steps when resonated
with a 27nH inductor. Figure 2 shows a Q enhancement
circuit.
Startup SequenceThe MAX1474 must be programmed before use. When
powered up, the following sequence must occur:Deassert both EN and DAT.Assert EN.Send pulses on DAT. The total number of pulses
determines the capacitance value (Table 1).Deassert EN.
Applications InformationThe MAX1474 offers users a wide range of applica-
tions, including trimming of regenerative receivers,
oscillators, RFID tags, and capacitive sensors. A
capacitive sensor is usually made of two capacitors.
One capacitor (CM) changes with the sensed function,
such as pressure, acceleration, or humidity. The sec-
ond capacitor (CR) is used as a reference capacitance
that does not vary with the sensed function. In most
applications, it is needed to detect the difference
between these capacitance values. Due to manufactur-
ing tolerances, there are normally offsets between CM
and CR, which can easily be nulled out by the FLECAP
as shown in Figure 4.
To increase the adjustment capacitance range, several
FLECAPs can be placed in parallel. Several capacitors
can be tied together to increase the number of steps or
the resolution, as shown in Figures 5a and 5b.
The FLECAP zero step differential capacitance is low,
typically 0.42pF. The parasitic capacitances are the
reason for the 6pF of input capacitance and the
decrease in range when configured as a single-ended
capacitor. The MAX1474 is an excellent choice in appli-
cations where only differential capacitance matters.
Table 1. Capacitance Values
MAX1474
Miniature Electronically Trimmable CapacitorFigure 1. Digital Timing Diagram
Figure 2. Q Enhancement Circuit
Test Circuits/Timing DiagramsFigure 3a. Capacitance vs. Voltage (Single Ended)
