mc13150ftb Lansdale Semiconductor, Inc., mc13150ftb Datasheet - Page 4

• Manufacturer Part Number: mc13150ftb
• Description: Narrowband Fm Coilless Detector If Subsystem
• Manufacturer: Lansdale Semiconductor, Inc.

ML13150
GENERAL DESCRIPTION
The ML13150 is a very low power single conversion nar-
rowband FM receiver incorporating a split IF. This device
can be used as a single conversion or as the backend in
analog narrowband FM systems such as 900 MHz cord-
less phones, and narrowband data links with data rates up
to 9.6 k baud. It contains a mixer, oscillator, extended
range received signal strength indicator (RSSI), RSSI
buffer, IF amplifier, limiting IF, a unique coilless quadra-
ture detector and a device enabler function (see Package
Pin Outs/Block Diagram).
LOW CURRENT OPERATION
The ML13150 is designed for battery and portable
applications. Supply current is typically 1.7 mAdc at 3.0
Vdc. Figure 2 shows the supply current versus supply
voltage.
ENABLE
The enable function is provided for battery powered
operation. The enabled pin is pulled down to enable the
regulators. Figure 3 shows the supply current versus
enable voltage, V enable (relative to V CC ) needed to
enable the device. Note that the device is fully enabled at
V CC - 1.3 Vdc. Figure 4 shows the relationship of the
enable current, I enable, to enable voltage, V enable .
MIXER
The mixer is a double-balanced four quadrant multiplier
and is designed to work up to 500 MHz. It has a single
ended input. Figure 5 shows the mixer gain and saturated
output response as a function of input signal drive and for
–10 dBm LO drive level. This is measured in the applica-
tion circuit shown in Figure 15 in which a single LC
matching network is used. Since the single–ended input
impedance of the mixer is 200 Ω, and alternate solution
uses a 1:4 impedance transformer to match the mixer to
50 Ω input impedance. The linear voltage gain of the
mixer alone is approximately 4.0 dB (plus an additional
6.0 dB for the transformer). Figure 6 shows the mixer
gain versus the LO input level for various mixer input
levels at 50 MHz RF input.
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ML13150 CIRCUIT DESCRIPTION
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The buffered output of the mixer is internally loaded,
resulting in an output impedance of 1.5kΩ.
LOCAL OSCILLATOR
The on–chip transistor operates with crystal and LC
resonant elements up to 220 MHz. Series resonant,
overtone crystals are used to achieve excellent local
oscillator stability. 3rd overtone crystals are used through
about 65 to 70 MHz. Operation for 70 MHz up to 200
MHz is feasible using the on–chip transistor with a 5th or
7th overtone crystal. To enhance operation using an
overtone crystal, the internal transistor's bias is increased
by adding an external resistor from Pin 29 (in 32 pin QFP
package) to V EE to keep the oscillator on continuously or
it may be taken to the enable pin to shut is off when the
receiver is disabled. –10 dBm of local oscillator drive is
needed to adequately drive the mixer (Figure 6). The
oscillator configurations specified above are described in
the application section.
RSSI
The received signal strength indicator (RSSI) output is a
current proportional to the log of the received signal
amplitude. The RSSI current output is derived by
summing the currents from the IF and limiting amplifier
stages. An external resistor at Pin 25 (in 32 pin QFP
package) sets the voltage range or swing of the RSSI
output voltage. Linearity of the RSSI is optimized by
using external ceramic bandpass filters which have an
insertions loss of 4.0 dB. The RSSI circuit is designed to
provide 100+ dB of dynamic range with temperature
compensation (see Figures 7 and 23 which show the RSSI
response of the applications circuit).
RSSI BUFFER
The RSSI buffer has limitations in what loads it can
drive. It can pull loads well towards the positive and
negative supplies, but has problems pulling the load away
from the supplies. The load should be biased at half
supply to overcome this situation.
LANSDALE Semiconductor, Inc.
Issue A