Today’s cars are equipped with an increasing number of electronic systems for various purposes and all need to be supplied from a primary voltage source to a lower secondary source. Power management is usually performed by an on-board power supply, but external sensors and modules must be wired throughout the vehicle and are exposed to harsh conditions. It must be ensured that the main power supply remains operational in the event of a failure in the off-board devices and that the ECU processor or other essential circuits continue to perform its task. Therefore, it is a popular measure to use so-called Voltage Trackers, such as the R1540 just released by Ricoh, where a reference voltage is replicated with high tracking accuracy and the safety level of the electronic system is generally increased. A secondary advantage is the shared heat dissipation since the total load is now shared between the Voltage Regulator and Voltage Tracker.
A regulator output voltage may vary due to electromagnetic noise interference (EMI), advanced technology is built-in to prevent such voltage variation. According to severe tests conducted in our laboratories, it has been confirmed that the R1540 has superior immunity to EMI noise over a broad frequency band (150 kHz to 1 GHz). Furthermore, it has a high ripple rejection ratio of 80 dB and a fast response to transients on input and load. The R1540 has a stable operation, it is essential to use a ceramic output capacitor with a minimum value of 10 μF.
Wide Operating Voltage Range:
The new CMOS-based R1540 is robust enough to survive in harsh conditions; it operates up to 42 V and has a maximum rating of 50 V. It even tolerates load dump surge peak voltages of 60 V with a duration of less than 200 ms. The minimum operating voltage starts at 3.5 V, which makes the R1540 suitable to use even at severe cranking conditions. The product will be available in a version targeted for the consumer, industrial and automotive application market and has customized operating temperature ranges for each purpose, respectively –40 to 105 °C, –50 to 125 °C and –40 to 125 °C. As for the automotive version, it is scheduled to become AEC-Q100 compliant soon. The output voltage is internally fixed by laser trimming and can be set in a range from 2.2 to 14 V.
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| Typical Application Schematic. |
Protection Circuits:
The R1540 has a series of safety features that protect the IC and other parts of the application from possible damage and defects.
- Over-current protection, limiting the output current in the event of overload.
- Short protection, detects a short circuit and decreases the output current to a safe level.
- Thermal protection, turns off the output voltage when an excess temperature of 165 °C is detected and will resume to normal operation again as soon a temperature of 135 °C is reached.
- Protected pin lay-out, a special lay-out was arranged for the R1540S in HSOP-8E package preventing a malfunction when adjacent pins were shorted. All four terminals are isolated with unconnected adjacent pins.
To be used in:
Target applications for this voltage tracker are for example automotive or industrial applications with sensors or modules. The R1540 is available in two packages; a regular SOT-23-5 and larger HSOP-8E package. Samples and evaluation boards are available through our worldwide regional distributor network as well as online distributors Mouser and Chip1Stop.
Conclusion
The new R1540 voltage tracker is a brand new product in our product range and is a welcome addition to our portfolio of automotive solutions. Remarkable features are its robust immunity against EMI noise and ability to respond fast to line and load transients. This makes the R1540 a reliable voltage source for use in noise critical devices.
