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NXP Semiconductors DEMO1985MC34940E
- Part No.:
- DEMO1985MC34940E
- Manufacturer:
- NXP Semiconductors
- Category:
- Sensor Evaluation Boards
- Package:
- Datasheet:
-
DEMO1985MC34940E.pdf
- Description:
- KIT DEMO FOR MC34940E FAMILY
- Quantity:
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Product details
Overview
DEMO1985MC34940E from Freescale Semiconductor is an electric field imaging device designed for non-contact proximity and capacitive touch sensing. It generates a tunable low-frequency sine wave (60–240 kHz), supports up to 7 electrode channels with selectable routing via ABC logic inputs, and delivers DC-level output proportional to capacitance changes at the electrode interface. It is used in appliance control panels, liquid level sensing, and industrial safety systems requiring robust E-field detection.
For engineers reviewing the DEMO1985MC34940E datasheet, DEMO1985MC34940E pinout, DEMO1985MC34940E application, or DEMO1985MC34940E equivalent, key selection criteria include oscillator frequency tuning via ROSC resistor, LPF response time adjustment via LPCAP capacitor, electrode signal harmonic suppression (<−20 dB), shield driver capability for coaxial electrode routing, and compatibility with 9–18 V VPWR supply.
Technical Context
The DEMO1985MC34940E integrates a precision sine-wave oscillator (tunable 60/120/240 kHz), 7-channel analog multiplexer for electrode selection, synchronous rectifier, gain-and-offset amplifier, and shield driver circuitry. Its internal voltage regulators generate separate analog (VDD) and digital (VCC) supplies from a single 9–18 V VPWR input.
Electrode signals are processed through a low-pass filter formed by internal resistance and external LPCAP capacitor (typical 10 nF → 2.5 ms response), while harmonic content is suppressed to <−20 dB (2nd–4th) and <−60 dB (5th+) to minimize interference. Shield enable (SHIELDEN) activates buffered AC signal drive to coaxial shields or ground planes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Frequency | Tunable 60/120/240 kHz via ROSC resistor; 120 kHz optimized for linear 10–70 pF range. |
| Electrode Count | 7 independent electrode terminals (E1–E7); selected via 3-bit ABC logic input. |
| Harmonic Suppression | ≤−20 dB (2nd–4th harmonics), ≤−60 dB (5th+), enabling clean E-field measurement. |
| Supply Voltage | 9–18 V VPWR; internally regulated to analog (VDD) and digital (VCC) rails. |
| Response Time | Adjustable via LPCAP capacitor: 500 µs (1 nF) to 2.5 ms (10 nF) typical settling. |
| Shield Driver | Active when SHIELDEN = high; drives coaxial shield or ground plane with matched-phase signal. |
| Output Signal | LEVEL pin provides amplified/offset DC voltage inversely proportional to electrode capacitance. |
Pinout & Package
DEMO1985MC34940E is housed in a 24-terminal SOICW package (Case 751E-04), with exposed thermal pad and Pb-free EG suffix compliant with RoHS.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| DGND (Pin 1) | Digital ground return | Reference for digital logic and internal VCC regulator; separate from AGND. |
| N/C (Pins 2, 24) | No connect | Must remain unconnected; no internal connection or function. |
| SHIELDEN (Pin 3) | Shield driver enable | High-active control: enables shield driver output on SHIELD pin. |
| C, B, A (Pins 4–6) | Electrode selection address | 3-bit binary code selects one of E1–E7; 000 disables all electrodes. |
| LEVEL (Pin 7) | Processed output signal | DC voltage representing detected capacitance; scaled and offset for MCU ADC input. |
| LPCAP (Pin 8) | Low-pass filter node | External capacitor sets response time; forms RC filter with internal 50 kΩ detector output resistance. |
| ROSC (Pin 9) | Oscillator frequency set | Resistor to ground sets center frequency: 20 kΩ → 240 kHz, 39 kΩ → 120 kHz, 82 kΩ → 60 kHz. |
| VDDCAP (Pin 10) | Analog supply filter | 47 µF capacitor stabilizes internal analog regulator output (VDD). |
| VPWR (Pin 11) | Main power input | 9–18 V supply; powers internal regulators and oscillator; withstands 26.5 V double-battery surge. |
| VCCCAP (Pin 12) | Digital supply filter | 47 µF capacitor stabilizes internal digital regulator output (VCC). |
| AGND (Pin 13) | Analog ground return | Reference for analog circuitry including detector, gain stage, and oscillator. |
| SHIELD (Pin 14) | Shield driver output | Buffered replica of electrode AC signal; cancels cable capacitance when connected to coax shield. |
| GND (Pin 15) | Main IC ground | Primary ground reference; connects to system ground plane and external 0 V. |
| TEST (Pin 16) | Test mode enable | Must be tied to GND for normal operation; floating or high may activate test modes. |
| E1–E7 (Pins 17–23) | Electrode interfaces | Seven independent transmit/receive nodes; each driven with low-harmonic sine wave and sensed for capacitance change. |
Key Features
| Feature | Design Value |
|---|---|
| 7-electrode multiplexing | Reduces system component count vs. discrete sensor ICs; enables compact multi-zone touch or proximity arrays. |
| Shield driver with SHIELDEN control | Eliminates noise coupling in long coaxial runs; allows remote electrode placement without signal degradation. |
| Tunable oscillator frequency | Three discrete bands (60/120/240 kHz) support trade-offs between sensitivity, range, and noise immunity per application. |
| Adjustable LPF response time | Capacitor-selectable settling time (500 µs to 2.5 ms) balances dynamic response against noise rejection. |
| High-purity sine generation | Low harmonic distortion ensures accurate capacitance-to-voltage conversion without spectral contamination. |
Applications
| Appliance Control Panels | Liquid Level Sensing |
|---|---|
|
Use Scenario: Capacitive touch buttons and sliders on refrigerator, oven, or washing machine control surfaces. IC Role / Device Role / Timing Role: Electric field imaging device generating and detecting 120 kHz excitation across embedded electrodes beneath panel surface. Use Value: Enables sealed, waterproof user interfaces with no mechanical wear; immune to moisture, dust, and cleaning agents. |
Use Scenario: Non-invasive detection of fluid height in transparent or opaque tanks (e.g., coffee makers, HVAC condensate reservoirs). IC Role / Device Role / Timing Role: Measures capacitance shift between parallel plate electrodes as liquid level changes dielectric constant from air (k=1) to water (k=80). Use Value: Eliminates moving parts and seals; supports continuous monitoring without tank penetration or calibration drift. |
| Garage Door Safety Sensing | Industrial Proximity Wake-Up |
|
Use Scenario: Obstacle detection zone at garage door bottom edge to prevent entrapment during closure. IC Role / Device Role / Timing Role: Drives shielded electrode strip along door edge; detects conductive or high-dielectric objects within ~5 cm via capacitance increase. Use Value: Provides fail-safe, contactless safety interlock compliant with UL 325; unaffected by dirt, ice, or paint buildup. |
Use Scenario: Low-power wake-up trigger for industrial HMI or IoT edge devices when operator approaches within sensing range. IC Role / Device Role / Timing Role: Operates in low-duty-cycle mode with adjustable ROSC/LPCAP to minimize quiescent current (7 mA typical) while maintaining fast response. Use Value: Extends battery life in portable equipment; enables instant UI activation without physical button press or optical sensor alignment. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar electric field imaging applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MC33794 | Single-chip E-field controller with integrated MCU interface; supports up to 16 electrodes; higher integration but fixed 120 kHz only. | Targeted at larger touch arrays (e.g., automotive center consoles); lacks ROSC/LPCAP tuning flexibility. | Select MC33794 when electrode count >7 and MCU co-location simplifies design; DEMO1985MC34940E preferred for tunable frequency and shield driver control. |
| AT42QT1070 | QTouch-based 7-channel capacitive controller; uses charge-transfer method; no external ROSC or shield driver; operates at ~1 MHz switching. | Optimized for PCB-mounted touch pads; unsuitable for long coaxial electrode runs or high-noise industrial environments. | Choose AT42QT1070 for cost-sensitive consumer touch panels; DEMO1985MC34940E remains superior for ruggedized, shielded, or liquid-immersed sensing. |
Compared with MC33794 and AT42QT1070, DEMO1985MC34940E uniquely combines tunable oscillator frequency, programmable LPF response, and active shield driver-enabling reliable E-field sensing across diverse mechanical layouts, environmental conditions, and dielectric media.
Availability
DEMO1985MC34940E is available at Aetrix Electronics and suitable for appliance control panels, liquid level sensing, and industrial safety systems requiring stable component supply and long-term lifecycle support.
Supply support for DEMO1985MC34940E includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Freescale Semiconductor (now part of NXP Semiconductors) was a leading designer of embedded processors and analog/mixed-signal ICs for automotive, industrial, and consumer applications.
The MC34940 product line was developed specifically for robust, low-cost electric field imaging in non-contact proximity and capacitive sensing systems where environmental resilience and design flexibility are critical.
FAQ
What is the primary function of the DEMO1985MC34940E?
The DEMO1985MC34940E is an electric field imaging device that generates a low-frequency sine wave and detects capacitance changes induced by nearby objects. It routes excitation to up to seven electrodes, processes returned signals into a DC voltage on the LEVEL pin, and supports shielded sensing via its dedicated SHIELD driver. This enables reliable non-contact detection in applications like touch panels and liquid level sensors.
How is the operating frequency set on the DEMO1985MC34940E?
The DEMO1985MC34940E oscillator frequency is set by an external resistor connected from ROSC (Pin 9) to ground. A 39 kΩ resistor yields 120 kHz (nominal), 20 kΩ yields 240 kHz, and 82 kΩ yields 60 kHz. These values are specified for 5% tolerance resistors and directly determine the excitation frequency applied to selected electrodes.
Can the DEMO1985MC34940E drive electrodes over long coaxial cables?
Yes-the DEMO1985MC34940E includes a shield driver activated by SHIELDEN (Pin 3). When enabled, SHIELD (Pin 14) outputs a buffered, phase-matched replica of the electrode AC signal, which cancels capacitive coupling along coaxial cables. This allows reliable operation with electrodes located up to several meters from the IC without signal degradation.
What is the role of the LPCAP pin on the DEMO1985MC34940E?
The LPCAP pin (Pin 8) forms a low-pass filter with internal detector resistance to smooth the rectified electrode signal. An external capacitor here determines system response time: 1 nF gives ~500 µs settling, while 10 nF gives ~2.5 ms. This allows designers to optimize noise rejection versus dynamic performance for each application.
Does the DEMO1985MC34940E require separate analog and digital power supplies?
No-the DEMO1985MC34940E accepts a single 9–18 V VPWR supply (Pin 11) and internally regulates separate analog (VDD) and digital (VCC) rails. External 47 µF capacitors on VDDCAP (Pin 10) and VCCCAP (Pin 12) stabilize these outputs, while AGND (Pin 13) and DGND (Pin 1) provide isolated ground returns for optimal noise separation.
DEMO1985MC34940E Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- -
- Packaging:
- Box
- Product Status:
- Obsolete
- Sensor Type:
- Touch, Capacitive
- Sensing Range:
- -
- Interface:
- Analog
- Sensitivity:
- -
- Voltage - Supply:
- 9V ~ 18V
- Embedded:
- No
- Contents:
- Board(s)
- Utilized IC / Part:
- MC34940
DEMO1985MC34940E FAQ
1.How can I place an order for DEMO1985MC34940E through Aetrix?
Please submit a Request for Quotation (RFQ) for DEMO1985MC34940E on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for DEMO1985MC34940E reliable?
The price and inventory of DEMO1985MC34940E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DEMO1985MC34940E is usually 5 days.
3.What payment methods are accepted for DEMO1985MC34940E?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DEMO1985MC34940E transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DEMO1985MC34940E?
DEMO1985MC34940E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DEMO1985MC34940E order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for DEMO1985MC34940E?
For technical support, including DEMO1985MC34940E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DEMO1985MC34940E requirements.
6.How does Aetrix verify that DEMO1985MC34940E is sourced from the original manufacturer or authorized distributors?
All DEMO1985MC34940E products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that DEMO1985MC34940E meets industry standards.
7.What is the process for return or replacement of DEMO1985MC34940E?
All DEMO1985MC34940E units undergo pre-shipment inspection (PSI). If there is an issue with DEMO1985MC34940E, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The DEMO1985MC34940E part is unused and in its original packaging.
Return procedure for DEMO1985MC34940E:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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