Component - TIA V1.60

PSoC® Creator™ Component Data Sheet
Trans-Impedance Amplifier (TIA)
1.60
Features
•
Selectable conversion gain
•
Selectable corner frequency
•
Compensated for capacitive input sources
•
Adjustable power settings
•
Selectable input reference voltage
General Description
The Trans-Impedance Amplifier (TIA) component provides an opamp-based current to voltage
conversion amplifier with resistive gain and user-selected bandwidth. It is derived from the
SC/CT block.
The TIA is used to convert an external current to a voltage. Typical applications include the
measurement of sensors with current outputs such as photo-diodes. The conversion gain of the
TIA is expressed in ohms, with the available range between 20 K and 1.0 Megohms. Current
output sensors, such as photo-diodes often have substantial output capacitance. This requires
shunt feedback capacitance in the TIA in order to guarantee stability. The TIA has a
programmable feedback capacitor to meet this need and provide bandwidth limiting to reduce
broadband noise.
Input/Output Connections
This section describes the various input and output connections for the TIA. An asterisk (*) in the
list of I/Os indicates that the I/O may be hidden on the symbol under the conditions listed in the
description of that I/O.
Iin – Analog
The Iin is the input signal terminal. The Iin is the sum of currents from the global inputs, which
may include signals from a current output DAC.
Note This terminal name is Iin (capital i) not lin (lowercase l).
Cypress Semiconductor Corporation • 198 Champion Court • San Jose, CA 95134-1709 • 408-943-2600
Document Number: 001-65714 Rev. **
Revised December 14, 2010
Trans-Impedance Amplifier (TIA)
PSoC® Creator™ Component Data Sheet
Vref – Analog
Vref is the input terminal for a reference signal. The reference may be an internal reference,
internal VDAC value, or external signal.
Vout – Analog
Vout is the output signal terminal. Vout is determined by the following equation, where Rfb is
resistive feedback:
Vout = Vref - Iin * Rfb
Equation 1
Positive (from source) currents result in output voltage, which is negative with respect to Vref.
Negative (into source) currents result in output voltage, which is positive with respect to Vref.
Parameters and Setup
Drag a TIA component onto your design and double-click it to open the Configure dialog.
Figure 1. Configure TIA Dialog
Capacitive Feedback
This sets the capacitive feedback for the TIA. The capacitive feedback can be set to None,
1.3 pF, 3.3 pF, or 4.6 pF (default). The -3 dB frequency for the TIA is calculated from the product
of the values of resistive and capacitive feedback components.
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Document Number: 001-65714 Rev. **
PSoC® Creator™ Component Data Sheet
Trans-Impedance Amplifier (TIA)
Power
This sets the initial drive power of the TIA. The power determines the speed with which the TIA
reacts to changes in the input signal. There are four power settings; Minimum, Low, Medium
(default), and High. Minimum Power setting results in the slowest response time and High Power
the fastest. Minimum and Low Power settings have reduced drive currents and are not suitable
for the lower values of feedback resistor.
Resistive Feedback
This sets the nominal resistive feedback for the TIA. The resistive feedback may be selected
from the following set of allowed values (in ohms): 20k (default), 30k, 40k, 80k, 120k, 250k,
500k, and 1000k.
-3 db Frequency
This combobox is used to display the calculated value of bandwidth. This value depends upon
Resistor Feedback, Capacitive Feedback value and Power setting.
Placement
There are no placement specific options.
Resources
The TIA uses one SC/CT block. Typically, the Vref input is routed from a voltage reference, a
VDAC output or an externally supplied reference on a GPIO.
API Memory
(Bytes)
Digital Blocks
Analog Blocks
Datapaths
Macro
cells
Status
Registers
Control
Registers
Counter7
Flash
RAM
Pins (per
External I/O)
1 SC/CT Fixed
HW block
N/A
N/A
N/A
N/A
N/A
352
2
3
Application Programming Interface
Application Programming Interface (API) routines allow you to configure the component using
software. The following table lists and describes the interface to each function. The subsequent
sections cover each function in more detail.
Document Number: 001-65714 Rev. **
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Trans-Impedance Amplifier (TIA)
PSoC® Creator™ Component Data Sheet
By default, PSoC Creator assigns the instance name "TIA_1" to the first instance of a 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. For readability, the instance name used in the following table is "TIA".
Function
Description
void TIA_Start(void)
Powers up the TIA.
void TIA_Stop(void)
Powers down the TIA.
void TIA_SetPower(uint8 power)
Setsdrive power to one of four levels.
void TIA_SetResFB(uint8 res_feedback)
Sets the resistive feedback to one of 8 values.
void TIA_SetCapFB(uint8 cap_feedback)
Sets the capacitive feedback to one of 4 values.
void TIA_Sleep(void)
Stops and saves the user configurations.
void TIA_Wakeup(void)
Restores and enables the user configurations.
void TIA_Init(void)
Initializes or restores default TIA configuration.
void TIA_Enable(void)
Enables the TIA.
void TIA_SaveConfig(void)
Empty function. Provided for future usage.
void TIA_RestoreConfig(void)
Empty function. Provided for future usage.
Global Variables
Variable
TIA_initVar
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Description
Indicates whether the TIA has been initialized. The variable is initialized to 0 and set to 1 the first
time TIA_Start() is called. This allows the component to restart without reinitialization after the
first call to the TIA_Start() routine.
If reinitialization of the component is required, then the TIA_Init() function can be called before
the TIA_Start() or TIA_Enable() function.
Document Number: 001-65714 Rev. **
PSoC® Creator™ Component Data Sheet
Trans-Impedance Amplifier (TIA)
void TIA_Start(void)
Description:
Performs all of the required initialization for the component and enables power to the
amplifier. The first time the routine is executed, the resistive and capacitive feedback and
amplifier power are set based on the values provided during the configuration. When called to
restart the TIA following a TIA_Stop() call, the current component parameter settings are
retained.
Parameters:
None
Return Value:
None
Side Effects:
None
void TIA_Stop(void)
Description:
Turns off the TIA 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 this component should be powered up (by calling the TIA_Start() routine)
at all times. Do not call the TIA_Stop() function.
Parameters:
None
Return Value:
None
Side Effects:
Does not affect power, resistive or capacitive feedback settings
void TIA_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
TIA_MINPOWER
Minimum active power and slowest reaction time.
TIA_LOWPOWER
Low power and speed.
TIA_MEDPOWER
Medium power and speed.
TIA_HIGHPOWER
Highest active power and fastest reaction time.
Return Value:
None
Side Effects:
None
Document Number: 001-65714 Rev. **
Page 5 of 12
Trans-Impedance Amplifier (TIA)
PSoC® Creator™ Component Data Sheet
(void) TIA_SetResFB(uint8 res_feedback)
Description:
Set the amplifier resistive feedback value.
Parameters:
uint8 res_feedback: See table below for valid resistive feedback settings.
Gain Setting
Notes
TIA_RES_FEEDBACK_20K
Feedback resistor = 20k
TIA_RES_FEEDBACK_30K
Feedback resistor = 30k
TIA_RES_FEEDBACK_40K
Feedback resistor = 40k
TIA_RES_FEEDBACK_80K
Feedback resistor = 80k
TIA_RES_FEEDBACK_120K
Feedback resistor = 120k
TIA_RES_FEEDBACK_250K
Feedback resistor = 250k
TIA_RES_FEEDBACK_500K
Feedback resistor = 500k
TIA_RES_FEEDBACK_1000K
Feedback resistor = 1000k
Return Value:
None
Side Effects:
None
(void) TIA_SetCapFB(uint8 cap_feedback)
Description:
Set the amplifier capacitive feedback value.
Parameters:
uint8 cap_feedback: See table below for valid capacitive feedback settings.
Gain Setting
TIA_CAP_FEEDBACK_NONE
No capacitive feedback
TIA_CAP_FEEDBACK_1_3PF
Feedback capacitor = 1.3 pF
TIA_CAP_FEEDBACK_3_3PF
Feedback capacitor = 3.3 pF
TIA_CAP_FEEDBACK_4_6PF
Feedback capacitor = 4.6 pF
Return Value:
None
Side Effects:
None
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Notes
Document Number: 001-65714 Rev. **
PSoC® Creator™ Component Data Sheet
Trans-Impedance Amplifier (TIA)
void TIA_Sleep(void)
Description:
This is the preferred API to prepare the component for sleep. The TIA_Sleep() function saves
the current component state. Then it calls the TIA_Stop() function and calls TIA_SaveConfig()
to save the hardware configuration.
Call the TIA_Sleep() function before calling the CyPmSleep() or the CyPmHibernate()
function. Refer to the PSoC Creator System Reference Guide for more information about
power management functions.
Parameters:
None
Return Value:
None
Side Effects:
None
void TIA_Wakeup(void)
Description:
This is the preferred routine to restore the component to the state when TIA_Sleep() was
called. The TIA_Wakeup() function calls the TIA_RestoreConfig() function to restore the
configuration. If the component was enabled before the TIA_Sleep() function was called, the
TIA_Wakeup() function will also re-enable the component.
Parameters:
None
Return Value:
None
Side Effects:
Calling the TIA_Wakeup() function without first calling the TIA_Sleep() or TIA_SaveConfig()
function may produce unexpected behavior.
void TIA_Init(void)
Description:
Initializes or restores the component according to the customizer Configure dialog settings. It
is not necessary to call TIA_Init() because the TIA_Start() routine calls this function and is
the preferred method to begin component operation.
Parameters:
None
Return Value:
None
Side Effects:
All registers will be set to values according to the customizer Configure dialog.
void TIA_Enable(void)
Description:
Activates the hardware and begins component operation. It is not necessary to call
TIA_Enable() because the TIA_Start() routine calls this function, which is the preferred
method to begin component operation.
Parameters:
None
Return Value:
None
Side Effects:
None
Document Number: 001-65714 Rev. **
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Trans-Impedance Amplifier (TIA)
PSoC® Creator™ Component Data Sheet
void TIA_SaveConfig(void)
Description:
Empty function. Provided for future usage.
Parameters:
None
Return Value:
None
Side Effects:
None
void TIA_RestoreConfig(void)
Description:
Empty function. Provided for future usage.
Parameters:
None
Return Value:
None
Side Effects:
None
Sample Firmware Source Code
PSoC Creator provides numerous example projects that include schematics and example code
in the Find Example Project dialog. For component-specific examples, open the dialog from the
Component Catalog or an instance of the component in a schematic. For general examples,
open the dialog from the Start Page or File menu. As needed, use the Filter Options in the
dialog to narrow the list of projects available to select.
Refer to the "Find Example Project" topic in the PSoC Creator Help for more information.
Functional Description
The TIA is constructed from a generic SC/CT block. The topology is an opamp with a selectable
feedback resistor from the output to the inverting input. Optionally, a selectable feedback
capacitor can also be connected between the output and the inverting input. See the following for
TIA configurations.
Figure 2: TIA Configurations
with Capacitive Feedback
Page 8 of 12
without Capacitive Feedback
Document Number: 001-65714 Rev. **
PSoC® Creator™ Component Data Sheet
Trans-Impedance Amplifier (TIA)
The output voltage is controlled by adjusting the Rfb feedback resistor. (See the following figure.)
Rfb may be set to one of 8 values, between 20k and 1000k ohms, selectable in either the
parameter dialog or the using the TIA_SetResFB() API function.
Figure 3: TIA Schematic
The DC output level can be adjusted by adding current to the Iin terminal. Positive current (into
the terminal) pushes the output negative; negative current (pulling current from the terminal)
pushes the output positive. The source of the current may be an internal DAC.
The amplifier bandwidth is determined by the interaction between the feedback resistor Rfb and
the selection of the capacitor in parallel with Rfb. The capacitive feedback value Cfb can be set
to one of four values in either the parameter dialog or by using the TIA_SetCapFB() API function.
The -3 dB frequency for the amplifier is:
Freq - 3dB = 1 /( 2pR fbC fb )
Equation 2
DC and AC Electrical Characteristics
The following values indicate expected performance and are based on initial characterization
data. Unless otherwise specified in the tables below, all TA = 25°C, Vdda = 5.0V, Power HIGH,
Op-Amp bias LOW, output referenced to 1.024V.
Note Characteristic data table will be updated following silicon characterization.
Document Number: 001-65714 Rev. **
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Trans-Impedance Amplifier (TIA)
PSoC® Creator™ Component Data Sheet
TIA DC Specifications
Parameter
Description
VIOFF
Input offset voltage
Rconv
Conversion resistance
Conditions
Min
Typ
Max
Units
–
3.5
10
mV
R = 20K; 40 pF load
15
–
27
k
R = 30K; 40 pF load
22.5
–
40.5
k
R = 40K; 40 pF load
30
–
54
k
R = 80K; 40 pF load
60
–
108
k
R = 120K; 40 pF load
90
–
162
k
R = 250K; 40 pF load
187
–
338
k
R= 500K; 40 pF load
375
–
675
k
R = 1M; 40 pF load
750
–
1350
k
–
0.9
2.0
mA
Quiescent current
Figures
Histogram offset
18
16
Typical Operating Current vs Temp, Power = Minimum
1200
Occurance
1100
Idda uA
14
12
1000
10
900
8
800
6
4
700
2
600
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Vos mV
6.0
4.0
2.0
0.0
-2.0
-4.0
-6.0
0
500
-50
5.5V
3.3V
2.7V
1.71V
0
50
deg C 100
150
Document Number: 001-65714 Rev. **
PSoC® Creator™ Component Data Sheet
Trans-Impedance Amplifier (TIA)
Typical Operating Current vs Temp, Power = Low
Typical Operating Current vs Temp, Power = High
1200
1200
1100
1100
Idda uA
1000
1000
900
900
5.5V
3.3V
2.7V
1.71V
800
700
800
Idda uA
700
600
600
500
-50
500
-50
0
50
deg C 100
5.5V
3.3V
2.7V
1.71V
150
0
50
deg C 100
150
TIA AC Specifications
Parameter
BW
Description
Conditions
Input bandwidth (–3 dB)
Min
Typ
Max
Units
R = 20K; –20 pF load
1600
–
–
kHz
R = 120K; –20 pF load
240
–
–
kHz
R = 1M; –20 pF load
25
–
–
kHz
R = 20K; –40 pF load
1500
–
–
kHz
R = 120K; –40 pF load
240
–
–
kHz
R = 1M; –40 pF load
25
–
–
kHz
Figures
Voltage noise, Vdda = 5.0V, Power=High
1000
nV/rtHz
100
10
0.01
0.1
1
kHz
10
100
1000
Note More specifications at other voltages and graphs will be added after characterization.
Document Number: 001-65714 Rev. **
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Trans-Impedance Amplifier (TIA)
PSoC® Creator™ Component Data Sheet
Component Changes
This section lists the major changes in the component from the previous version.
Version
1.60
Description of Changes
Reason for Changes / Impact
Updated the Configure dialog.
Created a customized interface. Added calculated
bandwidth to customizer to support Bandwidth
display.
Removed Min-vdda parameter
Parameter for min Vdda is not required. Component
shall auto-recognize voltage setting and set blockinternal switch pump accordingly.
Updated TIA component symbol
TIA component symbol is updated to reflect Resistive
Feedback, Capacitive Feedback, Fcorner value.
Added characterization data to the datasheet.
Minor datasheet edits and updates
1.50
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.
TIA parameter Pull-down values are reordered The TIA parameter pull-down values are not in
in the ascending order.
ascending order. The 80kOhm comes after
1000k Ohm. Reordered the values accordingly.
Changed the minus symbol to be the same
length as horizontal stroke in the '+' character.
Updated the minus symbol to meet the industry
standard.
Updated a conditional statement to properly
The charge pump clock was not being enabled
enable the charge pump clock for PSoC 3 ES3 properly and therefore SC blocks were not working.
silicon and PSoC 5 ES2 silicon or later.
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Cypress does not assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in lifesupport systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems application
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Document Number: 001-65714 Rev. **
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