PSoC® Creator™ Component Data Sheet
Mixer
1.50
Features
•
Single-ended mixer
•
Adjustable power settings
•
Selectable reference voltage
•
Continuous time up mixing:
•
•
Input frequencies up to 500 kHz
•
Sample clock up to 1 MHz
Discrete time, sample & hold down mixing:
•
Input frequencies up to 14 MHz
•
Sample clock up to 4 MHz
General Description
The Mixer component provides a single-ended, non-precision mixer. The component offers two
configurations:
•
continuous time mode, used for multiply or up mixing
•
discrete time, sample and hold mode, used for sampled or down mixing.
The component accepts as inputs two signals at different frequencies and presents at the output
a mixture of signals at multiple frequencies, including the sum and difference of the input signal
and the local oscillator signal. Typically, the undesired frequency components in the output
signal are removed by filtering.
When to use a Mixer
The Mixer component can be used for frequency conversion of a given input signal using a fixed
local oscillator signal as the sampling clock.
The manipulations of signal frequencies performed by a mixer can be used to move signals
between frequency bands or to encode and decode signals. A mixer can be used to convert
signal power at one frequency into power at another frequency to make signal processing easier,
whether in hardware or software.
The mixer output can be used by filtering the desired signal harmonics using an off-chip filter or
the output can be used to drive an on-chip ADC through internal routing.
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Document Number: 001-60864 Rev. **
Revised August 11, 2010
Mixer
PSoC® Creator™ Component Data Sheet
Input/Output Connections
This section describes the input and output connections for the Mixer component. An asterisk (*)
in the list of I/Os indicats that the I/O may be hidden on the symbol under the conditions listed in
the description of that I/O.
Fin – Analog
Fin is the input signal terminal. The Fin signal is mixed with the local oscillator clock signal to
generate the Fout signal. Fin frequency is limited as follows:
•
Multiply (Up) Mixer
Fin < 500 kHz
•
Sample (Down) Mixer
Fin < 14 MHz
LO – Digital
LO is the local oscillator signal terminal. This signal serves as the sampling clock for the mixer.
The LO signal is mixed with the Fin signal to generate the Fout signal. For the Multiply Mixer
mode, the LO clock signal must have a duty cycle of 50%.
LO frequency is limited as follows:
•
Multiply (Up) Mixer
LO < 1 MHz
•
Sample (Down) Mixer
LO < 4 MHz
Vref – Analog
Vref is the input terminal for a reference voltage. The reference voltage may be one of the PSoC
internal reference sources, an internal VDAC value, or an external signal.
Fout – Analog
Fout is the output signal terminal. The Fout signal is the resultant signal of the mixing operation of
the Fin and LO signals.
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PSoC® Creator™ Component Data Sheet
Mixer
Component Parameters
Drag a Mixer component onto your design and double-click it to open the Configure dialog.
Figure 1: Configure Mixer Dialog
LO_Freq
This parameter is used to determine the appropriate values for the input and feedback resistance
of the mixer op-amp circuit. The parameter options are:
•
LO Freq less than 100 kHz – For local oscillator frequencies less than 100 kHz, 40 kΩ is
used for the input and feedback resistance.
•
LO Freq 100 kHz or greater – For local oscillator frequencies of 100 kHz or higher, the
resistance values are set to 20 kΩ.
Minimum Vdda
This parameter is determined by the minimum analog supply voltage expected for the PSoC in
the design. The parameter can be set to one of two values:
•
2.7 V or greater (default)
•
Less than 2.7 V
For an analog supply voltage below 2.7 V, the amplifier makes use of an internal boost circuit.
The component implementation uses an additional 10 MHz clock to drive the boost circuit for the
amplifier block.
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Mixer
PSoC® Creator™ Component Data Sheet
Mixer_Type
This parameter determines the configured mode of the mixer SC/CT block. The component
supports two mixer modes: Multiply (Up) Mixer and Sample (Down) Mixer.
Power
This sets the initial drive power of the mixer. The power determines the speed with which the
mixer reacts to changes in the input signal. There are four power settings; Minimum, Low,
Medium (default), and High. A Low Power setting results in the slowest response time and a
High Power setting results in the fastest response time.
Placement
There are no placement specific options.
Resources
The mixer uses one SC/CT block.
Application Programming Interface
Application Programming Interface (API) routines allow you to configure the component using
software. The following table lists each routine and provides a brief functional description. The
subsequent sections cover each function in more detail.
By default, PSoC Creator assigns the instance name "Mixer_1" to the first instance of the
component in a given design. You can rename it to any unique value that follows the syntactic
rules for identifiers. The instance name becomes the prefix of every global function name,
variable, and constant symbol associated with the component. For readability, the instance name
used in the following table is "Mixer".
Function
Description
void Mixer_Init(void)
Initializes or restores default Mixer configuration.
void Mixer_Enable(void)
Enables the Mixer.
void Mixer_Start(void)
Power up the Mixer.
void Mixer_Stop(void)
Power down the Mixer.
void Mixer_SetPower(uint8 power)
Set drive power to one of four levels.
void Mixer_Sleep(void)
Stops and saves the user configuration.
void Mixer_Wakeup(void)
Restores and enables the user configuration.
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PSoC® Creator™ Component Data Sheet
Mixer
Function
Description
void Mixer_SaveConfig(void)
Empty function. Provided for future usage.
void Mixer_RestoreConfig(void)
Empty function. Provided for future usage.
Global Variables
Variable
Mixer_initVar
Description
Indicates whether the Mixer has been initialized. The variable is initialized to 0 and set to 1 the
first time Mixer_Start() is called. This allows the component to restart without reinitialization after
the first call to the Mixer_Start() routine.
If reinitialization of the component is required, then the Mixer_Init() function can be called before
the Mixer_Start() or Mixer_Enable() function.
void Mixer_Init(void)
Description:
Initializes or restores default Mixer configuration.
Parameters:
None
Return Value:
None
Side Effects:
All registers will be reset to their initial values. This will re-initialize the component.
void Mixer_Enable(void)
Description:
Enables the Mixer.
Parameters:
None
Return Value:
None
Side Effects:
None
void Mixer_Start(void)
Description:
Performs all of the required initialization for the component and enables power to the block.
The first time the routine is executed, the input and feedback resistance values are
configured for the operating mode selected in the design. When called to restart the mixer
following a Mixer_Stop() call, the current component parameter settings are retained.
Parameters:
None
Return Value:
None
Side Effects:
None
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Mixer
PSoC® Creator™ Component Data Sheet
void Mixer_Stop(void)
Description:
Turn off the Mixer block.
Note This API is not recommended for use on PSoC 3 ES2 and PSoC 5 ES1 silicon. These
devices have a defect that causes connections to several analog resources to be unreliable
when not powered. The unreliability manifests itself in silent failures (e.g. unpredictably bad
results from analog components) when the component utilizing that resource is stopped. It is
recommended that all analog components in a design should be powered up (by calling the
<INSTANCE_NAME>_Start() APIs) at all times. Do not call the <INSTANCE_NAME>_Stop()
APIs.
Parameters:
None
Return Value:
None
Side Effects:
Does not affect mixer type or power settings
void Mixer_SetPower(uint8 power)
Description:
Sets the drive power to one of four settings; minimum, low, medium, or high.
Parameters:
(uint8) power: See the following table for valid power settings.
Power Setting
Notes
Mixer_MINPOWER
Lowest active power and slowest reaction time.
Mixer_LOWPOWER
Low power and speed.
Mixer_MEDPOWER
Medium power and speed.
Mixer_HIGHPOWER
Highest active power and fastest reaction time.
Return Value:
None
Side Effects:
None
void Mixer_Sleep(void)
Description:
Stops the component operation. Saves the configuration registers and the component enable
state. Should be called just prior to entering sleep.
Parameters:
None
Return Value:
None
Side Effects:
None
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PSoC® Creator™ Component Data Sheet
Mixer
void Mixer_Wakeup(void)
Description:
Restores the component enable state and configuration registers. Should be called just after
awaking from sleep.
Parameters:
None
Return Value:
None
Side Effects:
None
void Mixer_SaveConfig(void)
Description:
Empty function. Provided for future usage.
Parameters:
None
Return Value:
None
Side Effects:
None
void Mixer_RestoreConfig(void)
Description:
Empty function. Provided for future usage.
Parameters:
None
Return Value:
None
Side Effects:
None
Sample Firmware Source Code
The following is a C language example demonstrating the basic functionality of the mixer
component. This example assumes the component has been placed in a design with the default
name "Mixer_1."
Note If you renamed your component you must also edit the example code as appropriate to
match the component name you specified.
External Clock Oscillator
If the mixer component will be used with an external local oscillator signal, and the parameter
settings are configured during the project design phase, only a call to the associated Mixer
Start() routine is required to use this component.
#include <device.h>
void main()
{
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Mixer
}
PSoC® Creator™ Component Data Sheet
Mixer_1_Start();
LO Generated Internally
If the LO signal is generated internal to the PSoC, APIs to configure and start the LO clock must
also be called. The power setting for the Mixer_1 component can also be configured at run time.
#include <device.h>
#include "lo_clk.h"
void main()
{
/* Setup Local Oscillator Clock */
lo_clk_Enable();
lo_clk_SetMode(CYCLK_DUTY);
/* API Calls for Mixer Instance */
Mixer_1_Start();
Mixer_1_SetPower(Mixer_1_HIGHPOWER);
while (1)
{
}
}
Functional Description
Mixer functionality is implemented using the PSoC SC/CT block. The discrete time down mixer is
implemented using the switched capacitor mode. The multiplying (up) mixer uses the continuous
time block mode.
Discrete Time Down Mixer
The schematic for the internal configuration of the discrete time mixer is shown in the following
figure:
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PSoC® Creator™ Component Data Sheet
Mixer
Figure 2 Discrete Time Sample & Hold Mixer Schematic
The non-return-to-zero sample and hold is achieved by switching the integrating capacitor
between two capacitors. In Figure 2 above, either C1 or C4 can always be sampling the input
signal while the other is being integrated across the amplifier. The Fin signal is sampled at a rate
less than the Fin signal frequency. The mixer component is configured such that Fout is
integrated with a new value on the rising edge of the input clock.
For LO sample clock frequencies greater than half of the Fin signal frequency, the output is the
difference between the input and LO frequencies plus aliasing components. When the sample
clock frequency is less than half of the Fin signal frequency, the output is the difference between
the input and the largest integer multiple of the LO frequency that is less than the Fin signal
frequency.
For a given input carrier frequency, Fin, a sample LO clock frequency, Fclk, can be chosen to
provide the desired output frequency, Fout, for the system.
Provided that Fclk is less than 4MHz, and Fin is less than 14MHz:
If
If
2N − 1
Fclk < Fin < N ⋅ Fclk ,
2
2N + 1
N ⋅ Fclk < Fin <
Fclk ,
2
then
Fout = N ⋅ Fclk − Fin
Equation 1
then
Fout = Fin − N ⋅ Fclk
Equation 2
Equation 1 and Equation 2 can be summarized as:
Fout = abs ( N ∗ Fclk − Fin )
Equation 3
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Mixer
PSoC® Creator™ Component Data Sheet
Continuous Time Up Mixer
The schematic for the internal configuration of the continuous time mixer is shown below:
Figure 3: Continuous Time Mixer Configuration Schematic
In this mode the op-amp is configured as a PGA that uses the LO input signal to toggle between
an inverting PGA gain of 1 and a non-inverting unity gain buffer. The output signal includes
frequency components at Fclk ± Fin plus terms at odd harmonics of the LO frequency plus and
minus the input signal frequency: 3*Fclk ± Fin, 5*Fclk ± Fin, 7*Fclk ± Fin etc.
Fout = N * Fclk ± Fin
with N holding odd values
Equation 4
Frequency Planning
Note that proper frequency planning is required to achieve the desired Fout. As a minimum
requirement, the Nyquist criteria must be met for the desired Fout.
Fclk > 2 ∗ Fout
Equation 5
DC and AC Electrical Characteristics
The following values are indicative of expected performance and based on initial characterization
data. Unless otherwise specified in the tables below, all TA = 25°C, Vdd = 5.0 V, Power HIGH,
Opamp bias LOW, output referenced to 1.024 V.
Note Characteristic data table will be updated following silicon characterization.
DC Electrical Characteristics
Parameter
Typical
Min
Max
Units
Conditions and Notes
Offset Voltage
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PSoC® Creator™ Component Data Sheet
Parameter
Typical
Mixer
Min
Max
Units
1.3
10
mV
Input Current (linear)
Rfb = 20 kΩ
+/- 120
uA
Vdda = 5.0 V
Vref = Vdda/2
Linearity +/1 1%
Input Current (linear)
Rfb = 40 kΩ
+/- 2.5
uA
Vdda = 5.0 V
Vref = Vdda/2
Linearity +/1 1%
Output tri-stated
Input Offset Voltage
Conditions and Notes
Operating Current
Off
0
0.1
uA
Minimum Power
80
100
uA
400
500
uA
Min
Max
Units
Low Power
Medium Power
High Power
AC Electrical Characteristics
Parameter
Typical
Conditions and Notes
AC Electrical Characteristics
Slew Rate (20% to 80%)
Minimum Power
V/uS
Low Power
V/uS
Medium Power
V/uS
High Power
V/uS
CT Up Mixer
Sample Frequency
1.0
MHz
Signal Frequency
500
kHz
Sample Frequency
4.0
MHz
Signal Frequency
14
MHz
SC Down Mixer
Noise
Minimum Power
nV/√Hz
Low Power
nV/√Hz
Medium Power
nV/√Hz
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Mixer
PSoC® Creator™ Component Data Sheet
Parameter
Typical
Min
Max
High Power
CMRR
Units
Conditions and Notes
nV/√Hz
90
PSRR
60
at 1.0 kHz, 1.0 V headroom
69
dB
at 100 kHz, 1.0 V headroom
Component Changes
This section lists the major changes in the component from the previous version.
Version
1.50
Description of Changes
Reason for Changes / Impact
Added Sleep/Wakeup and Init/Enable
APIs.
To support low power modes, as well as to provide
common interfaces to separate control of initialization and
enabling of most components.
Updated Symbol and Configure dialog.
To comply with corporate standards.
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