HMC8100LP6JE Data Sheet
Rev. B | Page 18 of 27
THEORY OF OPERATION
The HMC8100LP6JE is a highly integrated intermediate
frequency (IF) receiver chip that converts radio frequency (RF)
to a single-ended IF signal at its output. The internal active gain
circuit (AGC) of the HMC8100LP6JE is able to actively level the
output power at the IF output via SPI control. The gain control of
the HMC8100LP6JE can be controlled externally as an
alternative option via the VC_VGA_RF and VC_VGA_IF pins
with voltages ranging from 3.3 V (minimum attenuation) to 0 V
(maximum attenuation).
The HMC8100LP6JE utilizes an input low noise amplifier
(LNA) cascaded with a variable gain amplifier (VGA), which
can either be controlled by the internal AGC or external
voltages, that feeds the RF signals to an image reject mixer. The
local oscillator port can either be driven single ended through
LON or differentially through the combination of LON and
L O P.
The radio frequency is then converted to intermediate
frequencies, which can either feed off chip via baseband
differential outputs or feed on chip into a programmable band-
pass filter. It is recommended during IF mode operation that
the baseband outputs be unconnected. The programmable
band-pass filter on chip has four programmable bandwidths
(14 MHz, 28 MHz, 56MHz, and 112 MHz). The programmable
band-pass filter has the capability to adjust the center frequency.
From the factory, a filter calibration is conducted and the center
frequency of the filter is set to 140 MHz. This calibration can be
recalled via SPI control or the customer can adjust the center
frequency, but the calibration value must be stored off chip (see
the Register Array Assignments section). An external filter
option can be utilized to allow the customer to select other filter
bandwidths/responses that are not available on chip. The
external filter path coming from the image reject mixer feeds
into an amplifier that has differential outputs. The output of the
external filter can be fed back into the chip, which is then
connected to another amplifier.
A VGA follows immediately after the band-pass filter. Control
the IF VGA either by the AGC or external voltages. The output
of the variable gain amplifier is the output of the device.
The SPI RESET pin on the HMC8100LP6JE must be held low
(Logic 0) during power on. This is critical for proper
programming and reliable operation. Apply a RESET low before
the bias voltage is applied to the device or use a pull-down
resistor on the RESET pin.
REGISTER ARRAY ASSIGNMENTS AND SERIAL
INTERFACE
The register arrays for the HMC8100LP6JE are organized into
nine registers of 16 bits. Using the serial interface, the arrays are
written or read one row at a time, as shown in Figure 50 and
Figure 51. Figure 50 shows the sequence of signals on the enable
(SEN), CLK, and data (SDI) lines to write one 16-bit array of data
to a single register. The enable line goes low, the first of 24 data
bits is placed on the data line, and the data is sampled on the
rising edge of the clock. The data line should remain stable for
at least 2 ns after the rising edge of CLK. The device supports a
serial interface running up to 10 MHz, the interface is 3.3 V
CMOS logic.
A write operation requires 24 data bits and 24 clock pulses, as
shown in Figure 50. The 24 data bits contain the 3-bit chip
address, followed by the 5-bit register array number, and finally
the 16-bit register data. After the 24th clock pulses of the write
operation, the enable line returns high to load the register array
on the IC.
A read operation requires 24 data bits and 48 clock pulses, as
shown in Figure 51. For every register read operation you must
first write to Register 7. The data written should contain the
3-bit chip address, followed by the 5-bit register number for
Register 7, and finally the 5-bit number of the register to be
read. The remaining 11 bits should be logic zeroes. When the
read operation is initiated, the data is available on the data
output (SDO) pin. The output data bits are placed on the data
line during the rising edge of the clock.
Read Example
If reading Register 2, the following 24 bits should be written to
initiate the read operation.
00000000000 00010 00111 110
ZERO BITS (11 BITS)
REGISTER 7 ADDRESS (5 BITS)
REGISTER TO BE READ (5 BITS)
CHIP ADDRESS (3 BITS)
13867-049
Figure 49. Sample Bits to Initiate Read