REF3033 PCB Design Guide: Footprint, Pinout, and Alternatives
Micropower 3.3 V precision series bandgap reference in SOT-23-3.
The REF3033 is the 3.3 V member of TI's REF30 family: a precision series bandgap voltage reference in a 3-pin SOT-23 that holds its output between 3.294 and 3.306 V (0.2 % max initial accuracy at 25 °C) while drawing 42 µA typical. Drift is 75 ppm/°C max over the full −40 °C to +125 °C range by the box method (50 ppm/°C max from 0 °C to 70 °C), it sources up to 25 mA, and unloaded dropout is 1 mV typ / 50 mV max, so the recommended input floor is only VOUT + 0.05 V. The current datasheet, SBVS032K Rev. K (December 2025), covers the whole REF30 and REF30E family in one document.
Pick the REF3033 when an ADC or DAC needs a stable 3.3 V full-scale reference on a microamp budget: it is far more accurate and quieter than the logic rail or an LDO output pressed into reference duty. Do not pick it as a power rail; 25 mA of source-only output is a reference, not a regulator. Do not connect it to anything above the 5.5 V recommended input maximum, because absolute max is only 7 V. And if the error budget needs better than 0.2 % and 75 ppm/°C, the drop-in REF3033E grade in the same package (±0.1 %, 15 ppm/°C max, 27 µA typ, 10 mA sink and source) is the upgrade path.
The recurring REF3033 board bugs are supply-side and expectation-side: powering it from the same 3.3 V rail it is supposed to improve on, hanging it on rails beyond its 7 V absolute maximum, expecting it to sink current it cannot sink, mishandling output capacitors it never needed in the first place, and quoting REF3033E table numbers for the plain part. Each is covered below.
What breaks boards
It cannot make 3.3 V from a 3.3 V rail: the 50 mV dropout is an unloaded spec
The headline dropout of 1 mV typ / 50 mV max applies with no load, and the recommended input minimum is VOUT + 0.05 V. Every loaded spec assumes more headroom: load regulation is defined at VIN = VREF + 500 mV. Powering a REF3033 from the 3.3 V logic rail it is supposed to reference puts it out of spec before bring-up starts; the output simply follows the sagging rail. Feed it from 5 V, or any rail up to the 5.5 V recommended maximum, and budget real headroom at load.
Absolute maximum input is 7 V: this is a 5 V-rail part
Recommended input tops out at 5.5 V and the absolute maximum from IN to GND is 7 V, so industrial and automotive rails need a pre-regulator ahead of the reference. Supply quality at turn-on matters too: TI warns that supply voltages below the specified levels can cause the REF30 to momentarily draw more than its typical quiescent current, and recommends a supply with a fast rising edge and low output impedance. A slow soft-start rail feeding the reference can show surprising startup current draw.
The output sources 25 mA but is not specified to sink anything
The REF30 load-current spec is source-only: load regulation (3 ppm typ / 100 ppm max) is defined from 0 mA to 25 mA sourcing at VIN = VREF + 500 mV. Only the REF3033E grade is specified to sink (10 mA). If a downstream stage can push current back into the reference node, the output rises with nothing to pull it down. And 25 mA is a limit, not a use case: short-circuit current is 45 mA typ, absolute max is 70 mA, and dissipation in a SOT-23 with 297.3 °C/W junction-to-ambient feeds self-heating straight into the per-°C drift budget.
No output capacitor required, but big low-ESR ceramics deserve care
The REF30 does not require a load capacitor to be stable, and its electrical table is specified at ILOAD = 0 mA; with CL = 1 µF, turn-on settles to 0.1 % in 120 µs typ. If you do add a capacitive load, TI's application section says to take special care with low-ESR, high-capacitance capacitors. The input is a different story: always bypass IN with a low-ESR 0.1 µF ceramic at the pin, and note the power-supply section asks for more than 0.47 µF, so err on the larger side.
One datasheet, two grades: do not quote REF3033E numbers for the REF3033
SBVS032K covers the plain REF30 and the enhanced REF30E in separate electrical tables, and the E-grade numbers are much better: ±0.1 % initial accuracy, 15 ppm/°C max drift, 27 µA typ quiescent, 10 mA sink and source. The plain REF3033 gets the REF30 table: 0.2 % max, 75 ppm/°C max (−40 °C to +125 °C), 42 µA typ, source-only. Pulling the wrong row into an error budget is a spreadsheet-review classic. If the E numbers are the ones you need, order the REF3033E; it is a drop-in in the same SOT-23 (DBZ) package.
Key specifications
| Parameter | Value | Source |
|---|---|---|
| Output voltage / initial accuracy | VOUT 3.294 V min / 3.3 V typ / 3.306 V max; initial accuracy 0.2 % max (TA = 25C, VIN = 5V, ILOAD = 0mA) | SBVS032K Rev K, Section 6.6 REF30, REF3033 (3.3V) rows |
| Input voltage range | VOUT + 0.05 V min to 5.5 V max (REF30xx recommended); absolute maximum supply voltage, IN to GND: 7 V (REF30xx) | SBVS032K Rev K, Section 6.3 Recommended Operating Conditions + Section 6.1 Absolute Maximum Ratings |
| Quiescent current | 42 uA typ / 50 uA max (TA = 25C); 59 uA max (-40C <= TA <= 125C) | SBVS032K Rev K, Section 6.6 REF30 (continued), Power Supply, IQ rows |
| Temperature drift | 35 ppm/C typ / 75 ppm/C max (-40C <= TA <= +125C); 20 ppm/C typ / 50 ppm/C max (0C <= TA <= 70C); box method | SBVS032K Rev K, Section 6.6 REF30 (continued), dVOUT/dT rows |
| Dropout voltage | 1 mV typ / 50 mV max (VDO); recommended VIN min is VOUT + 0.05 V | SBVS032K Rev K, Section 6.6 REF30 (continued), VDO row + Section 6.3 footnote |
| Load current / load regulation | ILOAD 25 mA max (REF30xx, source only); load regulation 3 ppm typ / 100 ppm max (0mA < ILOAD < 25mA, VIN = VREF + 500mV) | SBVS032K Rev K, Section 6.3 Recommended Operating Conditions + Section 6.6 REF30 (continued), dVOUT/dILOAD row |
| Line regulation / output noise | Line regulation 130 uV/V typ / 400 uV/V max (VREF + 50mV <= VIN <= 5.5V); output voltage noise 36 uVpp (f = 10Hz to 1kHz), 105 uVrms (f = 10Hz to 10kHz) | SBVS032K Rev K, Section 6.6 REF30, REF3033 (3.3V) rows |
| Output capacitor / stability | No load capacitor required for stability; if a capacitive load is connected, take special care with low-ESR, high-capacitance capacitors; supply bypass capacitor of 0.1 uF always recommended (Section 8.1), supply bypass capacitor greater than 0.47 uF (Section 8.3) | SBVS032K Rev K, Section 3 Description + Section 8.1 Application Information + Section 8.3 Power Supply Recommendations |
| Thermal hysteresis / long-term stability | Thermal hysteresis 25 ppm typ / 100 ppm max; long-term stability 24 ppm typ (0000h to 1000h), 15 ppm typ (1000h to 2000h) | SBVS032K Rev K, Section 6.6 REF30 (continued), thermal hysteresis + long-term stability rows |
| Turn-on settling / short-circuit current | Turnon settling time 120 us typ (to 0.1% with CL = 1 uF); short-circuit current 45 mA typ; absolute maximum output short-circuit current 70 mA (short circuit to ground) | SBVS032K Rev K, Section 6.6 REF30 (continued), turnon settling time + ISC rows + Section 6.1 Absolute Maximum Ratings |
| Thermal resistance / operating temperature | RthetaJA junction-to-ambient 297.3 C/W (REF30xx, DBZ SOT-23, 3 pins); operating temperature -40C to +125C | SBVS032K Rev K, Section 6.4 Thermal Information + Section 6.3 Recommended Operating Conditions |
Verified against the manufacturer datasheet on 2026-07-10. Confirm the current revision before production use.
Alternatives
- REF3033E: the drop-in enhanced grade in the same SOT-23 (DBZ) package: ±0.1 % initial accuracy, 15 ppm/°C max drift (−40 °C to +125 °C), 27 µA typ quiescent, and it sinks as well as sources 10 mA. The upgrade when the error budget is tight.
- REF3330: TI's 3.3 V series reference in SOT-23 aimed at lower quiescent current at the cost of looser accuracy and drift; the common swap when battery life matters more than precision.
- ADR3433: Analog Devices' micropower 3.3 V series reference in SOT-23; the usual non-TI second source to compare on price and availability.
Common questions
- Can I power the REF3033 from a 3.3 V rail?
- No. The recommended input minimum is VOUT + 0.05 V even with no load (dropout is 1 mV typ / 50 mV max unloaded), and loaded specs like load regulation are defined at VIN = VREF + 500 mV. Run it from 5 V or any rail between those limits; the recommended maximum is 5.5 V and the absolute maximum is 7 V.
- Does the REF3033 need an output capacitor?
- No; the REF30 family does not require a load capacitor to be stable. If you add one, TI says to take special care with low-ESR, high-capacitance capacitors. The input should always be bypassed: a low-ESR 0.1 µF ceramic at the IN pin per the application section, with the power-supply section recommending more than 0.47 µF.
- What is the difference between the REF3033 and the REF3033E?
- Same function, same SOT-23 (DBZ) package, different grade. The REF3033E is specified at ±0.1 % initial accuracy, 15 ppm/°C max drift, 27 µA typ quiescent, and 10 mA of both sink and source; the plain REF3033 is 0.2 % max, 75 ppm/°C max, 42 µA typ, and source-only up to 25 mA. TI calls the E grade a drop-in replacement.
- How accurate is the REF3033 over temperature, really?
- Initial accuracy is 0.2 % max only at 25 °C (VOUT between 3.294 and 3.306 V). On top of that, budget 75 ppm/°C max drift from −40 °C to +125 °C (50 ppm/°C max over 0 °C to 70 °C), 100 ppm max load regulation over 0 to 25 mA, 400 µV/V max line regulation, 100 ppm max thermal hysteresis after temperature cycling, and 24 ppm typ long-term shift in the first 1000 hours.