ZRC330F01TA

The ZRC330F01TA is a precision 3.3 V shunt (parallel) voltage reference from Diodes Incorporated’s Zetex product line, offering ±1% initial accuracy in a compact SOT-23 (SC-59) surface-mount package. The -F01TA suffix denotes: F = SOT23 package, 01 = ±1% tolerance grade, TA = industrial temperature range tape & reel packaging.

Based on a bandgap circuit topology, the ZRC330 provides a stable 3.3 V reference voltage over an operating current range of 20 µA to 5 mA, with a typical knee current of just 15 µA. This ultra-low operating current makes it ideal for micropower and battery-powered applications where minimal quiescent current is critical. Unlike many bandgap references, the ZRC330 does not require an external stabilizing capacitor and remains inherently stable with any capacitive load, simplifying circuit design and reducing bill-of-materials cost.

The device’s robust design, based on 20 V processing technology, enables it to withstand transient currents up to 200 mA without damage – an important feature in real-world applications where power supply transients and inrush currents are common. Fast turn-on characteristics (settling in a few microseconds) make it suitable for switching applications and power-supply sequencing scenarios.

Performance specifications include a typical slope resistance of 0.6 Ω (max 2 Ω), dynamic impedance of 0.5 Ω at 150 µA bias, and output noise of 75 µVRMS across the 10 Hz to 10 kHz bandwidth. The temperature coefficient of 50 ppm/°C (max) over the -40°C to +85°C industrial range provides good stability across temperature variations.

The ZRC330 family offers three accuracy grades: -03 (±3%), -02 (±2%), and -01 (±1%, the highest precision). The SOT-23 package measures just 2.9 × 1.3 mm with 0.95 mm height, making it suitable for space-constrained designs. Green molding compound (bromine-free, antimony-free) and RoHS3 compliance support environmental requirements.

The ZRC330 is a two-terminal shunt (parallel) voltage reference that operates like a precision zener diode, but uses a bandgap reference circuit internally to achieve much better performance than a conventional zener. Here is how it works:

1. Bandgap Reference Core: At the heart of the ZRC330 is a bandgap voltage reference circuit. This circuit exploits the bandgap property of silicon, which has a known voltage of approximately 1.25 V at 0 K absolute zero. By combining two transistors with different current densities (one at high current density, one at low density), the bandgap circuit generates a voltage that is the sum of:
– A PTAT (Proportional To Absolute Temperature) voltage from the VBE difference of the two transistors
– A CTAT (Complementary To Absolute Temperature) voltage from the base-emitter voltage of one transistor
When these two opposing temperature coefficients are properly weighted and summed, the result is a temperature-independent reference voltage equal to the silicon bandgap voltage (extrapolated to 0 K) of approximately 1.25 V.

2. Gain Stage: Since the bandgap voltage is only about 1.25 V, an internal amplifier/gain stage scales this up to the target output voltage of 3.3 V. The gain is precisely trimmed during manufacturing to achieve the high initial accuracy (±1% for the 01 grade).

3. Two-Terminal Shunt Operation: The ZRC330 operates as a shunt regulator – it is connected in parallel (shunt) with the load, with a current-limiting resistor in series. When the cathode voltage tries to rise above 3.3 V, the internal circuit draws more current through the shunt path, pulling the voltage back down. Conversely, if the voltage drops, less shunt current is drawn, allowing the voltage to rise. This negative feedback mechanism maintains a precise 3.3 V across the device terminals.

4. Stability Without Capacitance: A key advantage of the ZRC330 design is its inherent stability without output capacitance. Many voltage references require an output capacitor for frequency compensation and stability. The ZRC330’s internal compensation ensures it is stable across the full operating current range and into any capacitive load, eliminating the need for external compensation components.

5. Low Knee Current: The knee current is the minimum current required for the reference to maintain its specified accuracy. With a typical knee current of only 15 µA, the ZRC330 can operate at very low current levels, making it suitable for micropower and battery-powered applications where power dissipation must be minimized.

6. Temperature Coefficient: The bandgap design achieves a low temperature coefficient (50 ppm/°C max) by balancing the positive temperature coefficient of the PTAT component against the negative temperature coefficient of the CTAT component, resulting in a near-zero net temperature coefficient at room temperature.

Pin Configuration (Top View, SOT-23):

  1 (VR/NC)
  |
.--+--.
|     |  2 (GND)
|     |
'--+--'
   |
   3 (VR Cathode)

Note: The ZRC330 is a two-terminal device functionally. Pin 1 is a no-connect in the SOT-23 package variant. The actual reference is between Pin 3 (cathode) and Pin 2 (anode/GND). Standard circuit application: supply voltage → series resistor → Pin 3 (cathode) → internal shunt → Pin 2 (GND) → ground. Output voltage is taken across Pin 3 and Pin 2.

Package: SOT-23-3 (TO-236-3 / SC-59). Body: 2.9 mm × 1.3 mm × 0.95 mm. Lead pitch: 0.95 mm. Gull-wing leads. 3000 pieces per 8 mm wide tape & reel. RoHS3 compliant. Green molding compound (halogen-free).

• Battery-Powered and Portable Equipment: Wearable devices, wireless sensors, IoT nodes, and portable instrumentation where the ultra-low operating current (20 µA minimum) extends battery life. The SOT-23 package’s small footprint fits into space-constrained portable designs, and no external capacitor requirement reduces board space and BOM cost.
• Precision Metering and Measurement Systems: Energy meters, flow meters, smart sensors, and data loggers requiring a stable voltage reference for ADCs and DACs. The ±1% initial accuracy and 50 ppm/°C temperature coefficient provide sufficient precision for many industrial metering applications without external calibration.
• Industrial Instrumentation: Process control transmitters, signal conditioners, and analog front-end modules where a stable reference voltage is needed for sensor excitation, analog-to-digital conversion, and threshold detection. The -40°C to +85°C industrial temperature range and 200 mA transient withstand capability ensure robust operation in industrial environments.
• Data Acquisition Systems: Multi-channel data acquisition boards, DAQ modules, and measurement instruments where the ZRC330 serves as a reference for ADCs or as a precision voltage source for sensor biasing. The fast settling time (microseconds) supports rapid multiplexing of multiple input channels.
• Precision Power Supplies and Regulators: As the voltage reference element in linear regulators, LDOs, and switching power supplies requiring a 3.3 V reference. The low dynamic impedance (0.5 Ω typical) and low slope resistance (0.6 Ω) ensure the reference voltage remains stable under varying load and line conditions.
• Crystal Oscillator Biasing: Temperature-compensated crystal oscillators (TCXOs), oven-controlled oscillators (OCXOs), and precision clock sources where a stable reference voltage for the oscillator circuitry is critical. The low output noise (75 µVRMS) minimizes phase noise contribution to the oscillator output.
• ADC/DAC Voltage References: Low-to-moderate resolution ADCs and DACs (8-12 bit) where the ZRC330 provides the reference voltage. The stable 3.3 V output matches common digital supply voltages, and the compact SOT-23 package allows placing the reference close to the converter for optimal performance.
• Overvoltage and Undervoltage Detection: Simple voltage monitoring circuits using a ZRC330 reference and a comparator to detect overvoltage or undervoltage conditions in power supplies, battery packs, and industrial equipment. The shunt topology works well with high-side sensing configurations.