Section 20. Comparator Voltage Reference

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1 Section 20. Comparator HIGHLIGHTS This section of the manual contains the following major topics: 20.1 Introduction Comparator Control egister Operation Interrupts I/O Pin Control Operation in Power-Saving and Debug Modes Effects of esets elated Application Notes evision History Comparator 2011 Microchip Technology Inc. DS61109F-page 20-1

2 PIC32 Family eference Manual Note: This family reference manual section is meant to serve as a complement to device data sheets. Depending on the device variant, this manual section may not apply to all PIC32 devices. Please consult the note at the beginning of the Comparator chapter in the current device data sheet to check whether this document supports the device you are using. Device data sheets and family reference manual sections are available for download from the Microchip Worldwide Web site at: INTODUCTION The Comparator module is a 16-tap, resistor ladder network that provides a selectable reference voltage. Although its primary purpose is to provide a reference for the analog comparators, it also may be used independently of them. A block diagram of the module is illustrated in Figure The resistor ladder is segmented to provide two ranges of voltage reference values and has a power-down function to conserve power when the reference is not used. The module s supply reference can be provided from either device VDD/VSS or an external voltage reference. The module output is available for the comparators and typically available for pin output. For more information, refer to the specific device data sheet. The Comparator has the following features: High and low range selection Sixteen output levels available for each range Internally connected to comparators to conserve device pins Output can be connected to a pin Figure 20-1: Comparator Block Diagram BGSEL<1:0> (1) VEF+ CVSS = 1 CVSC 1.2V 0.6V IVEF AVDD CVSS = 0 8 CV<3:0> VEFSEL (1) CVEN CVEFOUT 16 Steps 16-to-1 MUX CVCON<CVOE> CVEFOUT CV VEF- CVSS = 1 8 Note 1: AVSS CVSS = 0 These bits are not available on all devices. On such devices, CVEF is generated by the resistor network and IVEF is connected to 1.2V. efer to the specific device data sheet for availability. DS61109F-page Microchip Technology Inc.

3 Section 20. Comparator 20.2 COMPAATO VOLTAGE EFEENCE CONTOL EGISTE egister 20-1: ange 31/23/15/7 CVCON: Comparator Control egister 30/22/14/6 29/21/13/5 28/20/12/4 27/19/11/3 26/18/10/2 25/17/9/1 24/16/8/0 31:24 23:16 15:8 7:0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0 /W-0 U-0 U-0 U-0 U-0 /W-0 /W-0 /W-1 ON (1) VEFSEL (2) BGSEL<1:0> (2) U-0 /W-0 /W-0 /W-0 /W-0 /W-0 /W-0 /W-0 CVOE CV CVSS CV<3:0> Legend: = readable bit W = writable bit P = programmable r = reserved bit U = unimplemented bit, read as 0 -n = bit value at PO: ( 0, 1, x = unknown) bit Unimplemnted: ead as 0 bit 15 ON: Comparator On bit (1) 1 = Module is enabled, setting this bit does not affect other bits in the register. 0 = Module is disabled and does not consume current. Clearing this bit does not affect the other bits in the register bit Unimplemnted: ead as 0 bit 10 VEFSEL: Select bit (2) 1 =CVEF = VEF+ 0 =CVEF is generated by the resistor network bit 9-8 BGSEL<1:0>: Band Gap eference Source bits (2) 11 =IVEF = VEF+ 10 = eserved 01 = IVEF = 0.6V (nominal, default) 00 =IVEF = 1.2V (nominal) bit 7 Unimplemnted: ead as 0 bit 6 bit 5 bit 4 bit 3-0 CVOE: CVEFOUT Enable bit 1 = Voltage level is output on CVEFOUT pin 0 = Voltage level is disconnected from CVEFOUT pin CV: CVEF ange Selection bit 1 = 0 to 0.67 CVSC, with CVSC/24 step size 0 = 0.25 CVSC to 0.75 CVSC, with CVSC/32 step size CVSS: CVEF Source Selection bit 1 = Comparator voltage reference source, CVSC = (VEF+) (VEF-) 0 = Comparator voltage reference source, CVSC = AVDD AVSS CV<3:0>: CVEF Value Selection 0 CV<3:0> 15 bits When CV = 1: CVEF = (CV<3:0>/24) (CVSC) When CV = 0: CVEF =1/4 (CVSC) + (CV<3:0>/32) (CVSC) Note 1: When using 1:1 PBCLK divisor, the user s software should not read/write the peripheral s SFs in the SYSCLK cycle immediately following the instruction that clears the module s ON bit. 2: These bits are not available on all devices and the reset value is 0 for devices without these bits. efer to the specific device data sheet for availability. 20 Comparator 2011 Microchip Technology Inc. DS61109F-page 20-3

4 PIC32 Family eference Manual 20.3 OPEATION CVEF Output The Comparator module is controlled through the CVCON register (egister 20-1). This module provides two ranges of output voltage, each with 16 distinct levels. The range to be used is selected by the CV bit (CVCON<5>). The primary difference between the ranges is the size of the steps selected by the CVEF value selection bits, CV<3:0>, with one range offering finer resolution and the other offering a wider range of output voltage. The typical output voltages are listed in Table The equations used to calculate the CVEF output are as follows: If CV = 1: = ((CV<3:0>)/24) x (CVSC) If CV = 0: = (CVSC/4) + ((CV<3:0>)/32) x (CVSC) The CVEF Source Voltage (CVSC) can come from either VDD and VSS, or the external VEF+ and VEF- pins that are multiplexed with I/O pins. The voltage source is selected by the CVSS bit (CVCON<4>). The voltage reference is output to the CVEFOUT pin by setting the CVOE bit (CVCON<6>); this overrides the corresponding TIS bit setting. The settling time of the Comparator module must be considered when changing the CVEF output. For more information, refer to the specific device data sheet. Table 20-1: Typical in Volts (CVSC = 3.3) CV<3:0> CV = 0 (CVCON<5>) CV = 1 (CVCON<5>) V 0.00V V 0.14V V 0.28V V 0.41V V 0.55V V 0.69V V 0.83V V 0.96V V 1.10V V 1.24V V 1.38V V 1.51V V 1.65V V 1.79V V 1.93V V 2.06V DS61109F-page Microchip Technology Inc.

5 Section 20. Comparator CVEF Output Considerations The full range of voltage reference cannot be realized due to the construction of the module. The transistors on the top and bottom of the resistor ladder network (Figure 20-1) keep the voltage reference from approaching the reference source rails. The voltage reference is derived from the reference source. Therefore, the voltage reference output changes with fluctuations in that source. efer to the product data sheet for the electrical specifications. Table 20-2 contains the typical output impedances for the Comparator module. Table 20-2: CV<3:0> IVEF Output Typical CVEF Output Impedance in kilohms CV = 0 (CVCON<5>) CV = 1 (CVCON<5>) 0 12k 0.5k 1 13k 1.9k k 3.7k k 5.3k 4 15k 6.7k k 7.9k k 9k k 9.9k 8 16k 10.7k k 11.3k k 11.7k k 11.9k 12 15k 12k k 11.9k k 11.7k k 11.3k The Comparator module provides selection for the internal voltage reference. The Band Gap eference Source Select bits (BGSEL<1:0>) allow voltage selection of 1.2V or 0.6V, which is generated internally. efer to the specific device data sheet for the IVEF specifications. 20 Comparator 2011 Microchip Technology Inc. DS61109F-page 20-5

6 PIC32 Family eference Manual 20.4 INTEUPTS 20.5 I/O PIN CONTOL There are no Interrupt configuration registers or bits for the Comparator module. The module does not generate interrupts. The Comparator module can output to a pin. When the module is enabled and CVOE (CVCON<6>) is 1, the output driver for the CVEFOUT pin is disabled and the CVEF voltage is available at the pin. For operation, the TIS bit corresponding to the CVEFOUT pin must be a 1. This disables the digital Input mode for the pin and prevents undesired current draw resulting from applying an analog voltage to a digital input pin. The output buffer has very limited drive capability. An external buffer amplifier is recommended for any application that uses the CVEF voltage externally. An output capacitor may be used to reduce output noise. Use of an output capacitor will increase settling time (see Figure 20-2). Figure 20-2: Comparator Output Buffer Example Comparator Voltage eference Module (1) Voltage eference Output Impedance CVEF C (2) + Buffered Voltage eference Output Note 1: is dependent on the Comparator Control bits CV (CVCON<5>) and CV<3:0> (CVCON<3:0>). For more information, see Table : Use of an output capacitor will increase settling time. Capacitor value selection is dependent on the CV<3:0> and CV settings, and the frequency to be attenuated. DS61109F-page Microchip Technology Inc.

7 Section 20. Comparator 20.6 OPEATION IN POWE-SAVING AND DEBUG MODES Operation in Sleep Mode The Comparator module continues to operate in Sleep mode. The CVCON register is not affected when the device enters or wakes from Sleep mode. If the CVEF voltage is not used in Sleep mode, the module can be disabled by clearing the ON bit (CVCON<15>) prior to entering Sleep mode to save power Operation in Idle Mode 20.7 EFFECTS OF ESETS The Comparator module continues to operate in Idle mode. The CVCON register is not affected when the device enters or exits Idle mode. There is no provision to automatically disable the module in Idle mode. If the CVEF voltage is not used in Idle mode, the module can be disabled by clearing the ON bit (CVCON<15>) prior to entering Idle mode to save power Operation in Debug Mode The Comparator module continues to operate while the device is in Debug mode. The module does not support Freeze mode. All esets disable the voltage reference by forcing all bits in the CVCON register to Comparator 2011 Microchip Technology Inc. DS61109F-page 20-7

8 PIC32 Family eference Manual 20.8 ELATED APPLICATION NOTES This section lists application notes that are related to this section of the manual. These application notes may not be written specifically for the PIC32 family device family, but the concepts are pertinent and could be used with modification and possible limitations. The current application notes related to the Comparator module are: Title Application Note # elated application notes are not available. N/A Note: Please visit the Microchip web site ( for additional application notes and code examples for the PIC32 family of devices. DS61109F-page Microchip Technology Inc.

9 Section 20. Comparator 20.9 EVISION HISTOY evision A (October 2007) This is the initial released version of this document. evision B (October 2007) Updated document to remove Confidential status. evision C (April 2008) evised status to Preliminary; evised U-0 to r-x. evision D (June 2008) evised Figure 20-1; Change eserved bits from Maintain as to Write ; Added Note to ON bit (CVCON egister). evision E (August 2010) This revision includes the following updates: Updated the Comparator Block Diagram (see Figure 20-1) Added notes regarding the INV, SET, and CL registers to the Oscillators SF Summary (see Table 20-1) Updated the Comparator Control egister (see egister 20-1) emoved the CVCONINV, CVCONSET, and CVCONCL registers emoved Initialization Added new section IVEF Output emoved Table 20-4: Pins Associated with a Comparator emoved 20.8 Design Tips Minor corrections to formatting and text were incorporated throughout the document evision F (May 2011) This revision includes the following updates: Updated the Comparator Block Diagram (see Figure 20-1) emoved the Comparator SF Summary (Table 20-1) and related text Updated the BGSEL<1:0> bit value for 10 to eserved and modified the Notes in the CVCON register (see egister 20-1) Updated the allowable voltage reference selections in IVEF Output Minor updates to text and formatting were incorporated throughout the document 20 Comparator 2011 Microchip Technology Inc. DS61109F-page 20-9

10 PIC32 Family eference Manual NOTES: DS61109F-page Microchip Technology Inc.

Note the following details of the code protection feature on Microchip devices: Microchip products meet the specification contained in their particular Microchip Data Sheet.

11 Note the following details of the code protection feature on Microchip devices: Microchip products meet the specification contained in their particular Microchip Data Sheet. Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip s Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property. Microchip is willing to work with the customer who is concerned about the integrity of their code. Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as unbreakable. Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break Microchip s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. Information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICOCHIP MAKES NO EPESENTATIONS O WAANTIES OF ANY KIND WHETHE EXPESS O IMPLIED, WITTEN O OAL, STATUTOY O OTHEWISE, ELATED TO THE INFOMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PEFOMANCE, MECHANTABILITY O FITNESS FO PUPOSE. Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life support and/or safety applications is entirely at the buyer s risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights. Trademarks The Microchip name and logo, the Microchip logo, dspic, KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro, PICSTAT, PIC 32 logo, rfpic and UNI/O are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor, MXDEV, MXLAB, SEEVAL and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A. Analog-for-the-Digital Age, Application Maestro, CodeGuard, dspicdem, dspicdem.net, dspicworks, dsspeak, ECAN, ECONOMONITO, FanSense, HI-TIDE, In-Circuit Serial Programming, ICSP, Mindi, MiWi, MPASM, MPLAB Certified logo, MPLIB, MPLINK, mtouch, Omniscient Code Generation, PICC, PICC-18, PICDEM, PICDEM.net, PICkit, PICtail, EAL ICE, rflab, Select Mode, Total Endurance, TSHAC, UniWinDriver, WiperLock and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. SQTP is a service mark of Microchip Technology Incorporated in the U.S.A. All other trademarks mentioned herein are property of their respective companies. 2011, Microchip Technology Incorporated, Printed in the U.S.A., All ights eserved. Printed on recycled paper. ISBN: Microchip received ISO/TS-16949:2002 certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona; Gresham, Oregon and design centers in California and India. The Company s quality system processes and procedures are for its PIC MCUs and dspic DSCs, KEELOQ code hopping devices, Serial EEPOMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip s quality system for the design and manufacture of development systems is ISO 9001:2000 certified Microchip Technology Inc. DS61109F-page 20-11

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Section 40. Introduction (Part IV)

Section 40. Introduction (Part IV) HIGHLIGHTS This section of the manual contains the following major topics: 40.1 Introduction... 40-2 40.2 Revision History...40-3 40 Introduction (Part IV) 2007-2012