® PSoC Creator™ Component Datasheet Trans-Impedance Amplifier (TIA) 1.80 Features Selectable conversion gain Selectable corner frequency Compensation 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 photodiodes. The conversion gain of the TIA is expressed in ohms, with the available range between 20 k and 1.0 M . Current output sensors, such as photodiodes, often have substantial output capacitance. This requires shunt feedback capacitance in the TIA 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. It is the sum of currents from the global inputs, which may include signals from a current output DAC. Note This terminal name is Iin (uppercase i) not lin (lowercase l). Cypress Semiconductor Corporation • 198 Champion Court • San Jose, CA 95134-1709 • 408-943-2600 Document Number: 001-73946 Rev. ** Revised November 9, 2011 Trans-Impedance Amplifier (TIA) ® PSoC Creator™ Component Datasheet 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 R FB is resistive feedback: Vout = Vref – Iin × RFB Positive (from source) currents result in output voltage that is negative with respect to Vref. Negative (into source) currents result in output voltage that is positive with respect to Vref. Component Parameters Drag a TIA component onto your design and double-click it to open the Configure 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. Page 2 of 13 Document Number: 001-73946 Rev. ** ® PSoC Creator™ Component Datasheet 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 Power, Low Power, Medium Power (default), and High Power. The 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 on Resistor_Feedback, Capacitive_Feedback values and Power settings. 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. 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.” Document Number: 001-73946 Rev. ** Page 3 of 13 ® Trans-Impedance Amplifier (TIA) PSoC Creator™ Component Datasheet Function Description TIA_Start() Powers up the TIA. TIA_Stop() Powers down the TIA. TIA_SetPower() Sets drive power to one of four levels. TIA_SetResFB() Sets the resistive feedback to one of eight values. TIA_SetCapFB() Sets the capacitive feedback to one of four values. TIA_Sleep() Stops and saves the user configurations. TIA_Wakeup() Restores and enables the user configurations. TIA_Init() Initializes or restores default TIA configuration. TIA_Enable() Enables the TIA. TIA_SaveConfig() Empty function. Provided for future use. TIA_RestoreConfig() Empty function. Provided for future use. Global Variables Variable TIA_initVar 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. 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 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 Page 4 of 13 Document Number: 001-73946 Rev. ** ® PSoC Creator™ Component Datasheet Trans-Impedance Amplifier (TIA) void TIA_Stop(void) Description: Powers down TIA to its lowest power state and disables output. Note This API is not recommended for use on PSoC 3 ES2 and PSoC 5 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 (for example, unpredictably bad results from analog components) when the component using that resource is stopped. When using this silicon, all analog components in a design should be powered up (by calling their respective _Start() APIs, for instance TIA_Start()) at all times. Do not call the TIA_Stop() APIs. 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: 001-73946 Rev. ** Page 5 of 13 ® Trans-Impedance Amplifier (TIA) PSoC Creator™ Component Datasheet (void) TIA_SetResFB(uint8 res_feedback) Description: Set the amplifier resistive feedback value. Parameters: uint8 res_feedback: See the following table 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 the following table 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 Page 6 of 13 Notes Document Number: 001-73946 Rev. ** ® PSoC Creator™ Component Datasheet 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: 001-73946 Rev. ** Page 7 of 13 ® Trans-Impedance Amplifier (TIA) PSoC Creator™ Component Datasheet void TIA_SaveConfig(void) Description: Empty function. Provided for future use. Parameters: None Return Value: None Side Effects: None void TIA_RestoreConfig(void) Description: Empty function. Provided for future use. Parameters: None Return Value: None Side Effects: None Sample Firmware Source Code PSoC Creator provides many 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. Figure 1 shows the two possible TIA configurations. Figure 1. TIA Configurations with Capacitive Feedback Page 8 of 13 without Capacitive Feedback Document Number: 001-73946 Rev. ** ® PSoC Creator™ Component Datasheet Trans-Impedance Amplifier (TIA) The output voltage is controlled by adjusting the RFB feedback resistor (see Figure 2). RFB can be set to one of 8 values, between 20k and 1000k ohms, selectable in either the parameter dialog or using the TIA_SetResFB() API function. Figure 2. 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 can be an internal DAC. The amplifier bandwidth is determined by the interaction between the feedback resistor R FB 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 – 3 dB = 1/(2RFBCFB) Document Number: 001-73946 Rev. ** Page 9 of 13 ® Trans-Impedance Amplifier (TIA) PSoC Creator™ Component Datasheet DC and AC Electrical Characteristics for PSoC 3 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 = 5.0 V, High Power, Opamp bias low, output referenced to 1.024 V. TIA DC Specifications Parameter Description Conditions VIOFF Input offset voltage Rconv Conversion resistance Min Typ Max – 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 Units Figures Histogram Offset 18 16 Typical Operating Current versus Temp, Power = Minimum Occurance 1200 14 1100 Idda uA 12 1000 10 8 900 6 800 4 5.5V 3.3V 2.7V 1.71V 700 2 0 Page 10 of 13 Vos mV 6.0 4.0 2.0 0.0 -2.0 -4.0 -6.0 600 500 -50 0 50 deg C 100 150 Document Number: 001-73946 Rev. ** ® PSoC Creator™ Component Datasheet Trans-Impedance Amplifier (TIA) Typical Operating Current versus Temp, Power = Low Typical Operating Current versus 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 Input bandwidth (–3 dB) Conditions 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 = 5.0 V, Power=High 1000 nV/rtHz 100 10 0.01 0.1 1 kHz Document Number: 001-73946 Rev. ** 10 100 1000 Page 11 of 13 ® Trans-Impedance Amplifier (TIA) PSoC Creator™ Component Datasheet DC and AC Electrical Characteristics for PSoC 5 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 = 5.0 V, High Power, Opamp bias low, output referenced to 1.024 V. Note The characteristic data tables will be updated following silicon characterization. TIA DC Specifications Parameter Description VIOFF Input offset voltage RCONV Conversion resistance Conditions Min Typ Max – – 20 mV R = 20k; 40-pF load –25 – +35 % R = 30k; 40-pF load –25 – +35 % R = 40k; 40-pF load –25 – +35 % R = 80k; 40-pF load –25 – +35 % R = 120k; 40-pF load –25 – +35 % R = 250k; 40-pF load –25 – +35 % R= 500k; 40-pF load –25 – +35 % R = 1M; 40-pF load –25 – +35 % – 1.1 2 Min Typ Max R = 20k; 40-pF load 1000 – – kHz R = 120k; 40-pF load 230 – – kHz R = 1M; 40-pF load 23 – – kHz Quiescent current Units mA TIA AC Specifications Parameter BW Description Input bandwidth (–3 dB) Conditions Units Component Changes This section lists the major changes in the component from the previous version. Version 1.80 Description of Changes Modified source file to enable the charge pump when VDDA is below 2.7 V Reason for Changes / Impact Charge pump should be enabled below 2.7 V Added DC and AC Electrical characteristics data for PSoC 5 to datasheet Page 12 of 13 Document Number: 001-73946 Rev. ** ® PSoC Creator™ Component Datasheet Version 1.70 Description of Changes TIA_Stop() API modified for PSoC 5 Trans-Impedance Amplifier (TIA) Reason for Changes / Impact Changes required to prevent the component from impacting unrelated analog signals when stopped on PSoC 5 Added Debug window support 1.60 Added backward compatibility for register defines To provide backward compatibility for TIA_1_10. 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 will auto-recognize the voltage setting and set the block-internal 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 in the ascending order. The TIA parameter pull-down values are not in ascending order. The 80k ohm 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 enable the charge pump clock for PSoC 3 Production silicon and PSoC 5 ES2 silicon or later. The charge pump clock was not being enabled properly and therefore SC blocks were not working. © Cypress Semiconductor Corporation, 2011. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products in lifesupport systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. PSoC® is a registered trademark, and PSoC Creator™ and Programmable System-on-Chip™ are trademarks of Cypress Semiconductor Corp. All other trademarks or registered trademarks referenced herein are property of the respective corporations. Any Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide patent protection (United States and foreign), United States copyright laws and international treaty provisions. Cypress hereby grants to licensee a personal, non-exclusive, non-transferable license to copy, use, modify, create derivative works of, and compile the Cypress Source Code and derivative works for the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress integrated circuit as specified in the applicable agreement. Any reproduction, modification, translation, compilation, or representation of this Source Code except as specified above is prohibited without the express written permission of Cypress. Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to make changes without further notice to the materials described herein. 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 implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. Use may be limited by and subject to the applicable Cypress software license agreement. Document Number: 001-73946 Rev. ** Page 13 of 13