The HT1200M HART modem IC is a low-power modem chip designed for use in HART devices. It requires only a few external components to modulate and demodulate HART signals.
The HT1200M supports single, half-duplex 1200 bps frequency shift keying (FSK) and uses the Bell 202 FSK standard with 1200 Hz and 2200 Hz carriers. The device integrates a receive band-pass filter circuit and a transmit signal waveform shaping circuit.
HT1200M HART Modem IC Features
- Single, half-duplex 1200 bps FSK modem
- Bell 202 FSK with 1200 Hz and 2200 Hz carriers
- Integrated receive band-pass filter circuit
- Integrated transmit signal waveform shaping circuit
- External 460.8 kHz crystal or ceramic resonator for the internal clock oscillator, or external input clock
- Operating temperature: -40°C to +85°C
- Supply voltage: 2.7 V to 5.0 V
- Meets HART physical layer requirements
- LQFP32 and QFN32 packages
- Full compatibility with HT2015
1200 bps HART FSK Modem
The HT1200M is a 1200 bps half-duplex FSK modem.
The modem uses the Bell 202 FSK standard with:
- 1200 Hz carrier
- 2200 Hz carrier
The HT1200M integrates the receive band-pass filter and transmit signal waveform shaping functions required for HART signal modulation and demodulation.
HART Physical Layer
The HT1200M is designed for HART devices and meets HART physical layer requirements.
The device provides interfaces for transmitting and receiving HART signals, including the analog HART receive and transmit signal paths described in the pin definitions.
The OTXA output provides the modulated transmit signal and transmits the signal to the 4–20 mA loop. The IRXA input receives the FSK-modulated HART signal from the 4–20 mA loop interface circuit.
HT1200M Pin Configuration
The HT1200M is available in LQFP32 and QFN32 package types.
The device provides digital, analog, clock, reset and communication-related pins.
Main Pin Functions
| Pin | Name | Description |
|---|---|---|
| 1 | TEST5 | Connect to VSS |
| 2 | INRESET | Reset all digital logic circuits when input is low |
| 6 | VSS | Digital ground |
| 7 | OTXA | Modulated output transmit and transmit signal to 4–20 mA loop |
| 8 | IAREF | Analog reference voltage |
| 9 | ICDREF | Carrier detect reference voltage |
| 10 | OCBIAS | Comparator bias current |
| 12 | VSSA | Analog ground |
| 13 | VDDA | Analog supply voltage |
| 14 | IRXA | FSK-modulated HART receive signal from 4–20 mA loop interface circuit |
| 15 | ORXAF | Analog receive filter output |
| 16 | IRXAC | Analog receive comparator input |
| 17 | OXTL | Crystal oscillator output |
| 18 | IXTL | Crystal oscillator input |
| 21 | VDD | Digital power supply input |
| 22 | INRTS | Send request |
| 23 | ITXD | Input transmission data |
| 25 | ORXD | Received demodulated HART data transmitted to UART |
| 26 | OCD | Carrier detection output |
HART Transmit and Receive Interface
The HT1200M provides dedicated pins for HART signal transmission and reception.
HART Transmit Signal
The OTXA pin is used for the modulated output transmit signal and transmits the signal to the 4–20 mA loop.
HART Receive Signal
The IRXA pin receives the FSK-modulated HART signal from the 4–20 mA loop interface circuit.
The ORXAF pin provides the analog receive filter output, while IRXAC is the analog receive comparator input.
UART Data Interface
The ITXD pin receives the transmission data to be sent from the UART.
The ORXD pin outputs the received demodulated HART data to the UART.
Clock Configuration
The HT1200M supports an external 460.8 kHz crystal or ceramic resonator for the internal clock oscillator, or an external input clock.
The electrical characteristics section specifies the external clock frequency as:
460.8 kHz
with the documented oscillator deviation and duty-cycle parameters.
Electrical Characteristics
The HT1200M electrical characteristics are specified for:
VDD = 2.7 V to 5.5 V
VSS = 0 V
TA = -40°C to +85°C
Absolute Maximum Ratings
| Parameter | Min. | Max. | Unit |
|---|---|---|---|
| Environmental Temperature | -40 | +85 | °C |
| Storage Temperature | -55 | +150 | °C |
| Supply Voltage | 2.7 | 5.5 | V |
| DC Input and Output Voltage | -0.3 | VDD + 0.3 | V |
| Welding Temperature | — | 250 | °C |
DC Characteristics
The HT1200M DC characteristics include input voltage thresholds, output voltage characteristics, input capacitance, leakage current and supply current.
The documented supply current test condition is:
RBIAS = 500 kΩ
IAREF = 1.235 V
Under the specified test conditions, the supply current is listed with typical and maximum values in the electrical characteristics table.
AC Characteristics
The HT1200M AC characteristics specify the receive analog input, filter output, comparator input, transmit output and digital output characteristics.
For the IRXA receive analog input, the documented FSK logic frequencies include:
- Logic 1: 1200 Hz
- Logic 0: 2200 Hz
The corresponding frequency limits are provided in the manual’s AC characteristics table.
For the OTXA transmit output, the electrical characteristics include the specified frequency, amplitude, slope and loading parameters.
Modem Characteristics
The HT1200M modem characteristics include demodulator jitter specifications.
The documented test conditions include:
- Input frequency: 1200 Hz ±10 Hz and 2200 Hz ±20 Hz
- Clock frequency: 460.8 kHz ±0.1%
- Input asymmetry: 0
The demodulator jitter is specified as a percentage of one bit.
HT1200M Package Options
The HT1200M is available in two package types:
| Ordering Code | Package Type |
|---|---|
| HT1200M-L | LQFP32 |
| HT1200M-Q | QFN32 |
The ordering code structure identifies the package type using:
L = LQFP32
Q = QFN32
The manual provides HT1200M-L as an ordering example for the LQFP32 package.
HT1200M Circuit Diagram
The user manual provides a typical application circuit for the HT1200M HART modem ASIC.
The circuit diagram is provided in Chapter 6 Circuit Diagram as the HT1200M typical application circuit.
HT1200M Compatibility
The HT1200M is specified as fully compatible with HT2015.
HART Modem IC Technical Specifications
| Parameter | Specification |
|---|---|
| Device | HT1200M HART Modem ASIC |
| Modem Type | Single, half-duplex FSK modem |
| Data Rate | 1200 bps |
| FSK Standard | Bell 202 |
| Carrier Frequencies | 1200 Hz / 2200 Hz |
| Supply Voltage | 2.7 V–5.0 V |
| Electrical Characterization Supply Range | 2.7 V–5.5 V |
| Operating Temperature | -40°C to +85°C |
| Storage Temperature | -55°C to +150°C |
| Clock | 460.8 kHz external crystal/ceramic resonator or external input clock |
| Package | LQFP32 / QFN32 |
| HART Physical Layer | Meets HART physical layer requirements |
| Compatibility | Fully compatible with HT2015 |
Frequently Asked Questions
What is the HT1200M?
The HT1200M is a low-power HART modem ASIC that can be used in HART devices and requires only a few external components to modulate and demodulate HART signals.
What data rate does the HT1200M support?
The HT1200M is a 1200 bps half-duplex FSK modem.
Which FSK frequencies does the HT1200M use?
The HT1200M uses the Bell 202 FSK standard with 1200 Hz and 2200 Hz carriers.
What supply voltage does the HT1200M use?
The feature specification lists a supply voltage of 2.7 V to 5.0 V. The electrical characteristics are specified over a VDD range of 2.7 V to 5.5 V.
What is the operating temperature range?
The operating temperature range specified for the HT1200M is -40°C to +85°C.
Which package types are available?
The HT1200M is available in LQFP32 and QFN32 package types.
Is the HT1200M compatible with HT2015?
Yes. The manual specifies full compatibility with HT2015.
Does the HT1200M meet HART physical layer requirements?
Yes. The manual specifies that the HT1200M meets HART physical layer requirements.
HT1200M HART Modem ASIC User Manual
For detailed information on pin definitions, electrical characteristics, AC characteristics, modem characteristics, mechanical specifications, the typical application circuit and ordering code, refer to the HT1200M HART Modem ASIC User Manual.
Download the HT1200M User Manual
Contact Microcyber
For information about the HT1200M HART modem IC, package options and technical documentation, please contact Microcyber.
Request a Quote
