TPS613222ADBVR Boost Converter Design Guide: Battery-Powered 3.3 V Rail

Bottom Line: The TPS613222ADBVR is a 6-µA quiescent-current, 1.8-A switch-current boost converter that generates a stable 3.3 V or 5 V rail from a single-cell Li-ion or dual-AA battery. Three design decisions dominate real-world performance: (1) keep input capacitance ≥ 10 µF ceramic at the VIN pin to suppress input ripple below 50 mV, (2) select an inductor with a saturation current ≥ 2.2 A and DCR ≤ 150 mΩ to keep efficiency above 90 % at 500 mA load, and (3) follow TI's recommended PCB layout with a tight ground plane under the switching node to meet CISPR 32 Class B radiated-emission limits for portable products.

Overview of the TPS613222ADBVR

The TPS613222ADBVR is a fixed 3.3 V output, high-efficiency boost DC-DC converter from Texas Instruments housed in a 6-pin SOT-23 (DBV) package. It targets battery-powered portable devices where ultra-low quiescent current and a small BOM are mandatory. Operating from 0.9 V to 5.5 V input, it supports single-cell Li-ion (3.0–4.2 V), two AA/AAA alkaline cells (1.8–3.2 V), or a single Ni-MH cell (1.0–1.5 V). The sister parts TPS613221ADBVR (fixed 5 V) and TPS613223ADBVR (adjustable) use the identical footprint, so schematic re-spins cost nothing.

Peak efficiency reaches 95 % at 200 mA from a 3.6 V input, making the device competitive with any fixed-output boost on the market today. The 6 µA quiescent current in active regulation mode extends shelf life in wake-on-interrupt IoT nodes. A 1.8 A internal MOSFET switch eliminates the external switch component that discrete solutions require.

Input Capacitor Sizing

Input capacitor selection directly controls how much voltage droop appears on the battery rail during the switch ON phase. TI's SLVA585 application report recommends a minimum 10 µF X5R or X7R ceramic capacitor placed as close as possible to the VIN and GND pins. Voltage droop during peak switching scales with ESR: at 1.8 A switch current, a 10 mΩ ESR cap limits droop to 18 mV, while a 100 mΩ tantalum adds 180 mV—potentially triggering undervoltage lockout (UVLO engages below 0.85 V). Avoid Y5V and Z5U ceramics; their capacitance falls 70–80 % at the operating bias voltage, leaving effective capacitance well below the marked value.

For two-AA designs, where the ESR of alkaline cells can reach 0.5–2 Ω at end-of-life, add a second 10 µF capacitor in parallel. The combined low-ESR ceramic bank decouples the converter from the battery ESR, preventing oscillation in PFM (Pulse Frequency Modulation) mode at light loads. A 100 nF bypass in parallel absorbs high-frequency glitches generated by the switching transients.

Output Capacitor Selection

Output capacitance primarily governs output ripple and transient overshoot during load steps. The TPS613222ADBVR datasheet (SLVSAN6) recommends 22 µF minimum output capacitance with an ESR below 30 mΩ. A single 22 µF 0805 X5R ceramic rated at ≥ 6.3 V (for the 3.3 V output) is the simplest solution; derate to 50 % of rated voltage so effective capacitance remains ≥ 15 µF after DC bias derating. Output ripple voltage V_ripple ≈ ΔI_L × ESR, where ΔI_L is inductor ripple current. At 500 kHz switching frequency with a 22 µF / 10 mΩ ceramic, ripple stays under 5 mV pk-pk—well within the ±1 % regulation spec.

Load-step transients are more demanding: a 0-to-400 mA step with 22 µF output cap produces roughly 60 mV undershoot before the control loop recovers. Adding a second 22 µF cap in parallel halves this to 30 mV, which is acceptable for most microcontroller and sensor rails. Do not use bulk electrolytic capacitors as the sole output filter; their high ESR at MHz frequencies makes the boost loop unstable.

Inductor Selection Rules

The inductor is the most critical passive in a boost converter: wrong selection raises peak current above the MOSFET limit, saturates the core, and causes regulation loss. The TPS613222ADBVR operates at a fixed 500 kHz switching frequency (nominal), which constrains inductor choice to the 2.2 µH–4.7 µH range for most applications. Use the formula: L = (V_IN × (V_OUT − V_IN)) / (V_OUT × f_SW × ΔI_L), where ΔI_L is typically 30–40 % of peak inductor current. For V_IN = 3.6 V, V_OUT = 3.3 V, I_OUT = 500 mA, f_SW = 500 kHz: peak inductor current ≈ 1.3 A, recommending ΔI_L ≤ 0.5 A and L ≈ 2.2 µH.

Saturation current I_sat must exceed peak inductor current with margin: choose I_sat ≥ 2.2 A (120 % of 1.8 A switch limit). DCR directly impacts conduction loss; keep DCR ≤ 150 mΩ to hold efficiency above 90 %. Shielded inductors (e.g., Bourns SRR1210 or Murata LQH32CN series) are strongly preferred for portable designs because unshielded toroid inductors radiate significantly at 500 kHz and its harmonics, potentially violating FCC Part 15 or CISPR 32 limits. Self-resonant frequency (SRF) of the chosen inductor must exceed 10× the switching frequency—minimum 5 MHz SRF for reliable high-frequency filtering.

PCB Layout for Low-EMI Portable Devices

Compact, single-layer-friendly layout is possible with the SOT-23-6 package, but three layout rules are non-negotiable for low-EMI performance. First, place the input capacitor within 2 mm of VIN and GND pads; every millimeter of trace adds approximately 1 nH inductance that rings with switch-node capacitance. Second, keep the switching node (SW pin) copper area minimal—just enough to connect the inductor; excess copper acts as an antenna at 500 kHz and its harmonics. Third, route the feedback network (if using the adjustable TPS613223ADBVR variant) with the resistor divider away from the SW node to prevent switching noise injection into the FB pin.

A solid ground plane on the bottom layer under the IC reduces common-mode noise coupling into neighboring circuits. Stitch the top-layer GND island to the bottom plane with at least four vias. For two-layer boards, the input cap, IC, inductor, and output cap should form a compact rectangular loop to minimize loop area and magnetic field radiation. Per JEDEC JESD22-B101 board-level EMC guidance, prototype boards should be tested with a 1 GHz spectrum analyzer before PCB submission; common issues include 1st-harmonic spurs at 500 kHz and 3rd-harmonic spurs near 1.5 MHz.

Parameter	3.3 V / 200 mA IoT Node	3.3 V / 500 mA MCU Rail	5 V / 400 mA USB Peripheral
IC	TPS613222ADBVR	TPS613222ADBVR	TPS613221ADBVR
Input	1× Li-ion (3.0–4.2 V)	2× AA alkaline (1.8–3.0 V)	1× Li-ion (3.0–4.2 V)
Inductor	2.2 µH, I_sat ≥ 1.5 A	3.3 µH, I_sat ≥ 2.2 A	2.2 µH, I_sat ≥ 2.0 A
Input Cap	10 µF X5R + 100 nF	2× 10 µF X5R + 100 nF	10 µF X5R + 100 nF
Output Cap	22 µF X5R	2× 22 µF X5R	22 µF X5R
Efficiency (peak)	~95 %	~92 %	~91 %

Common Pitfalls and Troubleshooting

Pitfall 1 – Undersized Inductor Saturation Current: Using a 2.2 µH inductor rated at only 1.0 A I_sat causes the inductance to collapse at high load, pushing peak switch current beyond the 1.8 A limit and triggering current-limit hiccup mode. The symptom is a sputtering output voltage that recovers only when load is reduced. Correct approach: verify I_sat ≥ 2.2 A at the worst-case DC bias and temperature; many ferrite inductors lose 30 % of I_sat at 85 °C.

Pitfall 2 – Excessive Switching-Node Copper Area: A large ground-referenced copper pour connected to the SW pin acts as an antenna and couples 500 kHz noise into neighboring analog circuits. The consequence is elevated EMI floor at harmonics of the switching frequency, potentially failing CE/FCC pre-compliance scans. Correct approach: minimize SW copper to a small pad connecting the IC pin, inductor, and output diode (internal to the IC). Use a ground plane on the opposite layer beneath the IC to contain the magnetic field.

Pitfall 3 – Wrong Capacitor Dielectric (Y5V/Z5U): Y5V capacitors lose up to 82 % capacitance at rated DC voltage, turning a "22 µF" capacitor into an effective 4 µF at the 3.3 V rail. This increases ripple by 5.5× and can destabilize the control loop. Correct approach: always specify X5R or X7R ceramics for power supply bypass; verify the effective capacitance on a curve tracer or use a manufacturer's online derating tool.

Pitfall 4 – No Protection Against Reverse Current at Light Load: In PFM mode at very light loads (< 10 mA), the internal synchronous rectifier can allow slight reverse inductor current, causing audible switching-frequency noise in the 20–200 Hz range. While within datasheet specs, this surprises engineers expecting silent operation. Correct approach: if audible noise is unacceptable, add a small series Schottky (e.g., BAT54) at the output; accept the ~50 mV forward drop or switch to a true one-pulse-skip mode device.

Pitfall 5 – Input Capacitor Placed Remotely: Placing the input cap more than 5 mm from the IC VIN pin allows trace inductance to form an LC resonant tank with the bulk battery ESR, generating ringing that falsely triggers the UVLO. The output drops unexpectedly at moderate loads. Correct approach: place the input cap within 2 mm of VIN; if board constraints force distance, add a 10 Ω series resistor between the distant cap and VIN to damp the resonance.

FAQ

Q1: What is the minimum input voltage for the TPS613222ADBVR to produce a stable 3.3 V output? The TPS613222ADBVR starts up at 0.9 V and maintains regulation down to approximately 1.0 V input with load currents below 100 mA. At 500 mA output, minimum input is approximately 1.4 V due to switch duty-cycle limits (maximum duty cycle is ~90 %). For two-AA designs, the converter continues to regulate well past the point where alkaline cells are considered "dead" by conventional standards (typically 0.9 V/cell for a 1.8 V combined input).

Q2: How do I calculate the output current limit for a given input voltage? Use the power balance equation: I_OUT(max) = (η × V_IN × I_SW(max)) / V_OUT, where η is efficiency (~90 %), V_IN is minimum input voltage, and I_SW(max) is 1.8 A. At V_IN = 1.8 V: I_OUT(max) = (0.90 × 1.8 × 1.8) / 3.3 ≈ 882 mA theoretical, but practical limit is closer to 600 mA due to ripple current overhead. Derate by 20 % for thermal margin in enclosed enclosures.

Q3: Can the TPS613222ADBVR be used as a 3.3 V rail for an nRF52840 module with 32 MHz crystal and BLE radio? Yes. The nRF52840 peaks at approximately 15 mA during BLE TX bursts; the TPS613222ADBVR handles this comfortably with the dual 22 µF output cap absorbing the current transient. Ensure the crystal oscillator circuit is at least 10 mm from the SW pin to prevent 500 kHz switching noise from coupling into the 32 MHz oscillator. The 6 µA quiescent current makes the converter suitable for battery-powered BLE designs targeting 1–2 year coin-cell lifetimes.

Q4: What is the difference between TPS613221ADBVR, TPS613222ADBVR, and TPS613223ADBVR? All three share identical silicon, package, and switching specifications. The only difference is output voltage setting: TPS613221ADBVR is fixed 5 V, TPS613222ADBVR is fixed 3.3 V, and TPS613223ADBVR is adjustable via an external resistor divider on the FB pin (formula: V_OUT = 0.5 V × (1 + R1/R2)). All three are pin-compatible, so a single PCB layout covers all three output voltages. Search for all variants on FindMyChip to compare distributor pricing and stock levels.

Q5: What inductor brands are recommended for the TPS613222ADBVR in a compact 4-layer PCB? TI's reference design uses a Murata LQH32CN2R2M03L (2.2 µH, 1.5 A I_sat, 55 mΩ DCR, 0805 size) or equivalent. For higher output currents (up to 500 mA output), Bourns SRR1210-3R3Y (3.3 µH, 2.5 A I_sat, 85 mΩ DCR) provides extra headroom. Both are available through FindMyChip's verified distributor network; use the search page to compare spot pricing and lead times.

Conclusion

The TPS613222ADBVR is a highly capable boost converter for battery-powered 3.3 V applications, delivering up to 500 mA from input voltages as low as 1.0 V with 95 % peak efficiency and only 6 µA quiescent current. Successful design execution requires three things: correctly sized and biased X5R/X7R ceramics at input and output, a saturating-current-derated inductor with low DCR and high SRF, and a compact PCB layout that minimizes switch-node copper and maximizes ground-plane coverage. The sister parts TPS613221ADBVR (5 V) and TPS613223ADBVR (adjustable) extend the same design to other output voltages with no layout changes.

For procurement needs—whether engineering samples, production quantities, or hard-to-find inventory—FindMyChip connects you to 200+ verified distributors with 5-point authentication and 24-hour quote response. Visit the TPS613222ADBVR product page to compare real-time stock and pricing, or submit a quote request for volume orders with competitive China-origin pricing.