LMR33630ADDAR PCB Design Guide: Footprint, Pinout, and Alternatives
3 A synchronous buck converter for 3.8 V to 36 V inputs
LMR33630ADDAR is the large-reel orderable for the 400 kHz version of TI's LMR33630 synchronous buck converter in the eight-pin DDA package. It accepts 3.8 V to 36 V and provides an adjustable 1 V to 24 V output at up to 3 A. That range fits 12 V and 24 V rails, but the output still needs headroom below the input when the converter approaches dropout.
The device integrates both power MOSFETs, compensation, soft start, current limiting, thermal shutdown, and an open-drain power-good output. The exposed PowerPAD, input bypass loop, inductor choice, and actual ceramic capacitance still decide whether the board can deliver 3 A without excessive heat, ripple, or unstable transient response.
What breaks boards
Do not leave EN floating
TI allows EN to connect directly to VIN when precision enable is unused, but the pin must not float. A drifting EN node can leave the internal regulator in standby or repeatedly restart the converter.
Treat PG as an open-drain signal
The power-good output needs an external pullup. If PG is unused, TI says to leave it floating; do not drive it or assume it produces a logic-high voltage by itself.
Keep both input capacitors at the power loop
Provide at least 10 uF of ceramic input capacitance and place the required 220 nF bypass close to VIN and PGND. Remote bulk capacitance does not replace the local high-frequency current path.
Solder the PowerPAD into the thermal design
The DDA package's exposed pad must be soldered to PCB heat-spreading copper. Do not use the table's JEDEC RthetaJA value as a board-temperature prediction; TI says it is for package comparison, not application design.
Validate capacitance and loop response on hardware
Ceramic capacitance falls with DC bias, and TI limits total output capacitance to about ten times the calculated design value or 1000 uF, whichever is smaller. Check startup, load transients, and loop response on the assembled board.
Key specifications
| Parameter | Value | Source |
|---|---|---|
| Orderable identity | LMR33630ADDAR; active; 2500 devices per large tape-and-reel | TI LMR33630 product page metadata and SNVSAN3F orderable addendum, page 40 |
| Package | 8-pin HSOIC PowerPAD (DDA), 5.00 mm x 4.00 mm | SNVSAN3F Device Information, page 1; orderable addendum, page 40 |
| Converter type | Synchronous step-down DC/DC converter with adjustable output | SNVSAN3F title, Description, and Device Comparison Table, pages 1 and 4 |
| Input voltage | 3.8 V to 36 V recommended operating range | SNVSAN3F Recommended Operating Conditions, Table 7-1, page 6 |
| Output voltage | 1 V to 24 V adjustable output range | SNVSAN3F Recommended Operating Conditions, Table 7-1, page 6 |
| Output current | 0 A to 3 A recommended output-current range | SNVSAN3F Recommended Operating Conditions, Table 7-1, page 6 |
| Switching frequency | 340 kHz minimum, 400 kHz typical, 460 kHz maximum | SNVSAN3F Electrical Characteristics, Table 7-3, page 8, A version |
| Non-switching input current | 24 uA typical, 34 uA maximum with VFB = 1.2 V | SNVSAN3F Electrical Characteristics, Table 7-3, page 7 |
| Operating temperature | -40 degC to 125 degC operating junction-temperature range | SNVSAN3F Features and Electrical Characteristics, pages 1 and 7 |
| Minimum input capacitance | 10 uF minimum ceramic input capacitance plus a local 220 nF ceramic capacitor | SNVSAN3F Input Capacitor Selection, Section 9.2.2.6, page 23 |
Verified against the manufacturer datasheet on 2026-07-11. Confirm the current revision before production use.
Alternatives
- LMR33630ADDA: The same 400 kHz A-version and 8-pin DDA package supplied in a 75-piece tube instead of the ADDAR 2500-piece reel.
- LMR33630ARNXR: The 400 kHz A-version in a smaller 12-pin VQFN package. The footprint, pinout, and thermal path differ, so it is not a drop-in replacement.
- LMR33630BDDAR: The same 8-pin DDA package and 3 A rating with a 1.4 MHz switching frequency. Recalculate the inductor, switching losses, and EMI behavior before substitution.
Common questions
- Is LMR33630ADDAR the 400 kHz version?
- Yes. The A in the device option identifies the 400 kHz version. The B and C options switch at 1.4 MHz and 2.1 MHz nominal, so changing suffixes changes the power-stage design.
- What does the R suffix mean?
- LMR33630ADDAR is supplied as 2500 devices on a large tape-and-reel. LMR33630ADDA uses the same device option and package but comes in a 75-piece tube.
- Can LMR33630ADDAR deliver 3 A at every input and output voltage?
- No blanket guarantee follows from the 3 A rating. Duty cycle, ambient temperature, board copper, inductor limits, switching loss, and dropout all constrain the usable load. Check the data-sheet curves and verify the assembled power stage.
- How should unused power good be connected?
- Leave PG floating when it is unused. When used, add an external pullup to a suitable logic rail because PG is an open-drain output.
- Can the exposed pad be left unsoldered?
- No. The DDA PowerPAD is the main heat path into PCB copper. Solder it to the designed thermal copper and use the recommended land pattern and vias.
Sources
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