X9511 X9514 X9221 X9241 XK9241 X9312 X9313 X9314 X9C102/103/104/503 AN88-1

AN88 Evaluation Circuits for E2POTs by Gray Creager, June 1996 Introduction The use of Xicor's nonvolatile digital potentiometers

Application Note AN88 Evaluation Circuits for E2POTs by Gray Creager, June 1996 Introduction The use of Xicor's nonvolatile digital potentiometers 2 (E POTs) in mixed signal applications can offer a number of unique system advantages over the use of mechanical potentiometers. During prototyping, a design engineer may want to evaluate these devices in order to see how well they will perform in the intended application. In many cases, a simple circuit 2 to control an E POT's operation (and which can be "jumpered" into a target system) is sufficient. To that end, this application note features some simple circuit schematics that an engineer can build in order to 2 quickly evaluate any of Xicor's E POTs. PushPOTs The X9511 X9511 is a 32-tap, human interface, nonvolatile digital potentiometer with a direct pushbutton interface (i.e. PushPOT). This device provides added flexibility when designing consumer or industrial products which require user control of system parameters (e.g. LCD backlighting and contrast control on laptop computers). The PushPOT interface consists of separate PU and PD pins to control the movement of the wiper (respectively, up or down) Holding either pin LOW for a sufficiently long period of time allows the PushPOT to enter a slow wiper scan mode, which allows multiple wiper transistions without the need to pulse the pin HIGH between transitions. Continuing to hold the pin LOW will eventually initiate a fast wiper scan mode. Both of these pins are debounced and internally pulled-up, allowing for a direct pushbutton interface. The ASE pin (also debounced), when tied LOW during TM operation, implements a power-down AUTOSTORE mode which stores the current wiper position to 2 E PROM. Alternately, If this pin is normally HIGH during operation, but pulsed LOW when desired, a manual nonvolatile store cycle can be initiated. The X9514 X9514 is a log taper version of the X9511 X9511. The circuit in Figure 1 is adapted from the XK95 demo board and can be used to evaluate these devices. 2-Wire Serial Interface E2POTs 2 Xicor's dual and quad E POTs are available with an industry standard 2-wire serial interface. The X9221 X9221 is a dual 64-tap device and the X9241 X9241 is a quad 64-tap 2 device. Among other features, additional E PROM registers are contained within each device to allow for greater system flexibility (i.e. in order to store multiple wiper positions which can be recalled via software or to serve as a small amount of scratch nonvolatile memory for the system). The X9241 X9241 also allows for adjacent potentiometers to be internally cascaded, enabling the creation of a 256-tap potentiometer with only 3 redundant tap positions. The circuit in Figure 2 is adapted from the XK9241 XK9241 development system and can be used in conjunction with Xicor's XK9241 XK9241.EXE program to evaluate these devices. This code is available on Xicor's BBS, which can be reached toll free at 1-800-258-8864, or in the (408) area code and internationally at 1-408-943-0655. Xicor's BBS will support up to a 19.2K baud rate modem (no parity, 8 bit words, 1 stop bit, and no local echo). It can also be found on the World Wide Web (at the URL, http://www.xicor.com). 2 3-Wire E POTs A more traditional 3-wire interface, consisting of chip select (CS), increment (INC), and directional (U/D) pins, can be found on the X9CMME, X9312 X9312, X9313 X9313, and X9314 X9314. The X9CMME (aka X9C102/103/104/503 X9C102/103/104/503) has 100 taps and a tolerance on VH and VL of between -5V and +5V with respect to the Vss pin 2 voltage. This is standard for all of Xicor's E POTs, except for the X9312 X9312 which allows for any voltage between 0V and +15V (with respect to its' Vss pin voltage) to be applied to VH or VL. The X9CMME and X9312 X9312 have 100 taps, while the X9313 X9313 and X9314 X9314 have 32 taps. The X9314 X9314 is a log taper version of the X9313 X9313. The circuit in Figure 3 is adapted from the X9CMME demo board and can be used to evaluate these devices. Xicor, Inc. · 1511 Buckeye Drive · Milpitas, CA 95035 · (408) 432-8888 AN88-1 AN88-1 Xicor Application Note AN88 Table 1. E2POT Device Summary Part No. VH & VL Range Tap Positions End-to End Resistance () Vcc Packages* X9CMME X9312 X9312 X9313 X9313 X9314 X9314 X9511 X9511 X9514 X9514 ±5V 0V to 15V ±5V ±5V ±5V ±5V 100 100 32 32 32 32 1K, 10K, 50K, 100K 1K, 10K, 50K, 100K 1K, 10K, 50K, 100K 10K 1K, 10K 10K 3V - 5.5V 4.5V - 5.5V 3V - 5.5V 3V - 5.5V 4.5V - 5.5V 4.5V - 5.5V P8 D8 S8 P8 S8 P8 S8 M8 P8 S8 M8 P8 S8 P8 S8 X9221 X9221 ±5V 64 (dual) 2K, 10K, 50K 4.5V - 5.5V X9241 X9241 ±5V 64 (quad) 2K, 10K, 50K 4.5V - 5.5V Comments log taper PushPOT PushPOT, log taper 2 P20 S20 I C compatible, cascadeable 2 P20 S20 V20 I C compatible, cascadeable *Package code: P=plastic DIP, D=ceramic DIP, S=SOIC, M=MSOP, V=TSSOP, and the number indicates the number of pins/leads. Xicor package codes do not usually contain the pin/lead count so these abbreviations should not be used when ordering parts. VCC D1 R1 20K 1N5817 1N5817 U1 1 2 3 4 S1 PU PD VH VSS S2 VCC ASE VL VW 8 7 6 5 STORE S3 X9511 X9511 UP DOWN C1 VH VW VL 10uF Figure 1 - PushPOT evaluation circuit (with external AUTOSTORE circuitry). AN88-2 AN88-2 Xicor Application Note AN88 V CC V CC P1 1 14 2 15 3 16 4 17 5 18 6 19 7 20 8 21 9 22 10 23 11 24 12 25 13 R1 R2 4. 7K 4 .7 K U1 U2 F 14 9 12 13 3 1 2 VH0 VW0 VL 0 SC L SD A 8 6 7 VH1 VW1 VL 1 74 0 7 15 5 16 4 V H PO T 1 VW VL 11 13 12 VH2 VW2 VL 2 A3 A2 A1 A0 V H PO T 0 VW VL V H PO T 2 VW VL 17 19 18 VH3 VW3 VL 3 V H POT 3 VW VL X9241 X9241 P AR AL L E L P R IN T ER P O R T Figure 2 - X9221/X9241 X9221/X9241 evaluation circuit (to be used in conjunction with XK9241 XK9241.EXE). VCC U1 1N4 14 8 D1 U2B VCC 4 6 R3 R1 5 VH VW VL 3 5 6 VH VW VL 7 4HC132 4HC132 DOWN 0. 001 uF U2A 1 S2 I NC U/ D CS X9 CMME 27 K 10K 1 2 7 3 1N41 48 D2 C1 2 S1 U2C UP 74HC132 74HC132 R2 R4 10 8 1 0K 27 K 9 7 4HC1 32 R5 VCC 0.0 01uF C2 100K 0. 47 uF C3 Figure 3 - Simple 3-wire E2POT evaluation circuit. AN88-3 AN88-3