Overview
The ST485BD is a low-power transceiver designed for RS-485 and RS-422 communication, manufactured by STMicroelectronics. This device contains one driver and one receiver, making it suitable for half-duplex applications on multipoint bus transmission lines. It operates from a single 5 V supply and is characterized by its low quiescent current, drawing 300 μA (typical) when unloaded or fully loaded with disabled drivers. The ST485BD is available in various temperature ranges, including commercial (0 °C to 70 °C), industrial (-40 °C to 85 °C), and automotive (-55 °C to 125 °C).
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Supply Voltage | 5 V | V |
| Quiescent Current | 300 μA | μA |
| Propagation Delay | 30 ns | ns |
| Skew | 5 ns | ns |
| Common Mode Input Voltage Range | -7 V to 12 V | V |
| Input Hysteresis | 70 mV | mV |
| Driver Short-Circuit Current | 35 mA to 250 mA | mA |
| ESD Protection | ±15 kV (HBM), ±8 kV (IEC-1000-4-2) | kV |
| Maximum Data Rate | 5 Mbps | Mbps |
| Operating Temperature Range | -55 °C to 125 °C (automotive), -40 °C to 85 °C (industrial), 0 °C to 70 °C (commercial) | °C |
Key Features
- Operates from a single 5 V supply.
- Low quiescent current: 300 μA.
- 30 ns propagation delay, 5 ns skew.
- Allows up to 64 transceivers on the bus, or up to 256 transceivers in some variants.
- -7 V to 12 V common mode input voltage range.
- Designed for RS-485 interface application.
- 70 mV typical input hysteresis.
- Current limiting and thermal shutdown for driver overload protection.
- Driver maintains high impedance in 3-state or with the power OFF.
- ESD protection: ±15 kV (HBM), ±8 kV (IEC-1000-4-2).
Applications
The ST485BD is designed for bi-directional data communications on multipoint bus transmission lines, making it suitable for a variety of applications including:
- Industrial automation and control systems.
- Building automation and control systems.
- Automotive systems requiring robust communication interfaces.
- Point-of-sale terminals and other commercial equipment.
- Any system requiring reliable, low-power RS-485/RS-422 communication.
Q & A
- What is the typical quiescent current of the ST485BD?
The typical quiescent current of the ST485BD is 300 μA when unloaded or fully loaded with disabled drivers.
- What is the operating voltage range of the ST485BD?
The ST485BD operates from a single 5 V supply.
- What is the propagation delay of the ST485BD?
The propagation delay of the ST485BD is 30 ns, with a skew of 5 ns.
- How many transceivers can be connected on the bus?
The ST485BD allows up to 64 transceivers on the bus, though some variants can support up to 256 transceivers).
- What is the common mode input voltage range of the ST485BD?
The common mode input voltage range of the ST485BD is -7 V to 12 V).
- Does the ST485BD have ESD protection?
Yes, the ST485BD has ESD protection of ±15 kV (HBM) and ±8 kV (IEC-1000-4-2)).
- What are the operating temperature ranges for the ST485BD?
The operating temperature ranges for the ST485BD include -55 °C to 125 °C (automotive), -40 °C to 85 °C (industrial), and 0 °C to 70 °C (commercial)).
- How is the driver protected against overload?
The driver is protected against overload by current limiting and thermal shutdown circuitry that places the driver outputs into a high-impedance state).
- What is the maximum data rate supported by the ST485BD?
The maximum data rate supported by the ST485BD is 5 Mbps).
- Is the ST485BD suitable for automotive applications?
Yes, the ST485BD is suitable for automotive applications, with an operating temperature range of -55 °C to 125 °C).
