ML13155
LANSDALE Semiconductor, Inc.
CIRCUIT DESCRIPTION
The ML13155 consists of a wideband three–stage limiting
indicator (RSSI) circuit which provides a current output lin-
amplifier, a wideband quadrature detector which may be
early proportional to the IF input signal level for approxi-
operated up to 200 MHz, and a received signal strength
mately 35 dB range of input level.
Figure 2. Test Circuit
1.0n
Vin
49.9
1 IN1
2 DEC1
3 VCC1
4 DETO1
5 DETO2
6 VCC2
Limiter 1
Output
330
7 LIMO1
1.0n
8 QUAD1
QUAD2 9
IN2 16
10n
DEC2 15
VEE1 14
RSSI 13
Buffer
1.0k
RSSI 12
VEE2 11
LIMO2 10
1.0n
330
1.0n
1.0n
100n
Limiter 2
Output
10µ
VEE
VEE
+
VEE
+
1.0n
27
1.0n
100n
10µ
Video
Output
499
20p
L1
L1 – Coilcraft part number 146–09J08S
260n
APPLICATIONS INFORMATION
EVALUATION PC BOARD
The evaluation PCB shown in Figures 19 and 20 is very ver-
satile and is designed to cascade two ICs. The center section
of the board provides an area for attaching all surface mount
components to the circuit side and radial leaded components
to the component ground side of the PCB (see Figures 17 and
18). Additionally, the peripheral area surrounding the RF
core provides pads to add supporting and interface circuitry
as a particular application dictates. This evaluation board will
be discussed and referenced in this section.
LIMITING AMPLIFIER
Differential input and output ports interfacing the three stage
limiting amplifier provide a differential power gain of typical-
ly 46 dB and useable frequency range of 300 MHz. The IF
gain flatness may be controlled by decoupling of the internal
Page 3 of 16
feedback network at Pins 2 and 15.
Scattering parameter (S–parameter) characterization of the IF
as a two port linear amplifier is useful to implement maxi-
mum stable power gain, input matching, and stability over a
desired bandpass response and to ensure stable operation out-
side the bandpass as well. The ML13155 is unconditionally
stable over most of its useful operating frequency range; how-
ever, it can be made unconditionally stable over its entire
operating range with the proper decoupling of Pins 2 and 15.
Relatively small decoupling capacitors of about 100 pF have a
significant effect on the wideband response and stability.
This is shown in the scattering parameter tables where
S–parameters are shown for various values of C2 and C15
and at VEE of –3.0 and –5.0 V DC.
Issue A
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