500 °C Bipolar SiC Linear Voltage Regulator
Summary (2 min read)
Introduction
- Therefore, much research has been conducted in SiC electronics for elevated temperatures.
- This work was supported by the Swedish Foundation for Strategic Research through the HOTSiC Project.
- The feedback resistors (as a voltage–voltage network) sense the output, and a division of the sensed voltage is compared with the reference voltage.
A. Loop Gain Analysis
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B. Temperature Compensated Biasing
- The resistors values fall as temperature rises up to ∼200 °C.
- Assuming a constant biasing current for the OTA, decrease of the resistors RC1 and RC2 can significantly reduce the gain of the OTA.
- The biasing network can be designed in order to provide higher collector current for the gain stages as temperature increases.
- The current tail value for the OTA is derived from the equation of biasing network.
- (4) Considering the effect of Vbe (−2 mV/°C) and RE in (4), it is concluded that more tail current is available for the OTA at higher temperatures, which results in higher gain of the OTA.
C. Stability Issue
- The system has two poles; one of them is associated with the base of the pass device and the other one with the output of the regulator.
- Owing to the low output impedance of the pass device in emitter-follower configuration, the pole associated with the output of the regulator is pushed to high frequencies.
- The OTA has only one gain stage; there is no any other low-frequency node in the loop, and the stability of the voltage regulator can be inferred.
III. EXPERIMENTAL RESULTS AND DISCUSSIONS
- On-wafer characterization was performed on a temperaturecontrolled hot-stage.
- The measurements were conducted using either parameter analyzer or oscilloscope at each temperature.
A. Device Characterization
- A single BJT and the pass device were characterized individually.
- The pass device consists of four devices in parallel and compared with the single BJT provides higher collector current ratings, as can be observed in Fig. 3(b).
B. Circuit Characterization
- The feedback resistors ratio defines the relation between the output and the reference voltage: Vout = Vref · (1 + R f 1/R f 2).
- All of the measurements of this paper were performed with VCCOTA and Vin connected to the same power supply.
- The regulated voltage is fairly robust in the range 25 °C–500 °C. Fig. 4(b) presents the output variation in different load conditions.
- The load currents are measured at each temperature considering the temperature variation of the integrated resistors.
C. Performance Evaluation
- Line and load regulations [( Vout/ Vin), ( Vout/ Iload)] are two performance metrics of voltage regulators.
- The line regulation is calculated based on ±5% variation from the nominal input voltage.
- The load regulation follows a similar trend and remains in the range 2%–5% for the whole temperature range up to 500 °C.
- To measure the transient response of the regulator to instantaneous current loads, the output voltage was initially measured at a nominal input voltage (23 V).
- A 1-k on-chip resistor was used as the load, whose one end is connected to the output of the regulator and the other end is floated.
IV. CONCLUSION
- For 15 V output voltage and up to 15-mA load current, a stable output voltage with <2% variation with temperature is observed in the whole temperature range.
- In addition, the transient response of the regulator to a 15-mA load current shows no significant performance degradation with temperature increase.
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Citations
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Cites background from "500 °C Bipolar SiC Linear Voltage R..."
...As described earlier, lateral high-current 4H-SiC BJTs are required for a linear voltage regulator in bipolar SiC [254]....
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...A circuit that can benefit a lot from a lateral high-current BJT is a linear voltage regulator in bipolar SiC [252]–[254]....
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Cites background from "500 °C Bipolar SiC Linear Voltage R..."
...2: Comparison of this work with recent high temperature drivers in SiC NMOS and CMOS technologies NMOS SiC [14] NMOS SiC [52] CMOS SiC [22] Bipolar SiC (Batch....
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...Example of simple and complex circuits for extreme environments have been reported in MOSFET [12, 13, 14, 15], JFET[16, 17, 18], bipolar [19, 20, 21, 22], and CMOS[23, 24, 25, 26] technologies....
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...6 A high-current high-temperature SiC linear voltage regulator As discussed in [22], in order to add to the capability of the linear voltage regulator to supply heavier loads, a pass device with higher current capability is required....
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References
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...High-temperature integrated digital logic circuits [1], operational amplifiers [2], [3], and Schmitt triggers [4] are a few examples....
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"500 °C Bipolar SiC Linear Voltage R..." refers background in this paper
...High-temperature integrated digital logic circuits [1], operational amplifiers [2], [3], and Schmitt triggers [4] are a few examples....
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