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LTC3891EUDC#PBF
Public Unreviewedby Ray
Analog Devices DC-DC Controllers, QFN-20-EP(3x4). Datasheet-verified pinout, KiCad symbol/footprint/3D.
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Symbol & Footprint
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PCB Footprint
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Datasheet
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README
markdownLTC3891EUDC#PBF
Analog Devices · DC-DC Controllers · QFN-20-EP(3x4)
LTC3891EUDC#PBF from Analog Devices, in a QFN-20-EP(3x4). Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.
Pinout
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | PLLIN/MODE | input | External synchronization input to phase detector and forced continuous mode input. When an external clock is applied, the PLL forces rising TG to sync with the external clock rising edge and the regulator operates in forced continuous mode. Otherwise: tie to SGND for Burst Mode, float (internal 100k to GND) for Burst Mode, tie to INTVCC for forced continuous, or set 1.2V < V < INTVCC-1.3V for pulse-skipping. |
| 2 | SGND | power_in | Small-signal ground. Must be routed separately from high current grounds to the common (-) terminals of the CIN capacitor. Pins 2 and 3 must both be electrically connected to small signal ground. |
| 3 | SGND | power_in | Small-signal ground. Must be routed separately from high current grounds to the common (-) terminals of the CIN capacitor. Pins 2 and 3 must both be electrically connected to small signal ground. |
| 4 | RUN | input | Digital run control input. Forcing this pin below 1.16V shuts down the controller. Forcing it below 0.7V shuts down the entire LTC3891, reducing quiescent current to approximately 14μA. Absolute max -0.3V to 8V; max 100μA sourced into the pin from a source above 8V. |
| 5 | SENSE- | input | The (-) input to the differential current comparator. When greater than INTVCC - 0.5V, the SENSE- pin supplies power to the current comparator. Absolute max -0.3V to 28V. |
| 6 | SENSE+ | input | The (+) input to the differential current comparator. Normally connected to the DCR sensing network or current sensing resistor. The ITH pin voltage and controlled offsets between SENSE+ and SENSE- (in conjunction with RSENSE) set the current trip threshold. |
| 7 | VFB | input | Receives the remotely sensed feedback voltage from an external resistive divider across the output. Regulated to 0.800V typical (0.792V/0.808V min/max at 25°C). |
| 8 | ITH | output | Error amplifier output and switching regulator compensation point. The current comparator trip point increases with this control voltage. Absolute max -0.3V to 6V. |
| 9 | PGOOD | output | Open-drain logic output. PGOOD is pulled to ground when the voltage on the VFB pin is not within ±10% of its set point. Absolute max -0.3V to 6V. |
| 10 | TG | output | High current gate drive for top N-channel MOSFET. Output of the floating driver with a voltage swing equal to INTVCC superimposed on the switch node voltage SW. Pull-up Ron 2.5Ω typ, pull-down Ron 1.5Ω typ. |
| 11 | SW | power_out | Switch node connection to the inductor. Absolute max -5V to 65V. |
| 12 | BOOST | power_in | Bootstrapped supply to the topside floating driver. A capacitor is connected between BOOST and SW, and a Schottky diode is tied between BOOST and INTVCC. Voltage swing at BOOST is from INTVCC to (VIN + INTVCC). Absolute max -0.3V to 71V; BOOST-SW -0.3V to 6V. |
| 13 | BG | output | High current gate drive for bottom (synchronous) N-channel MOSFET. Voltage swing is from ground to INTVCC. Pull-up Ron 2.4Ω typ, pull-down Ron 1.1Ω typ. |
| 14 | INTVCC | power_out | Output of the internal linear low-dropout regulator (typ 5.1V). The driver and control circuits are powered from this voltage. Decouple to PGND with a minimum 2.2μF ceramic or other low-ESR capacitor. Do not use INTVCC for any other purpose. Absolute max -0.3V to 6V. |
| 15 | EXTVCC | power_in | External power input to an internal LDO connected to INTVCC. Supplies INTVCC power, bypassing the internal LDO powered from VIN, whenever EXTVCC is higher than 4.7V. Do not float or exceed 14V on this pin. Absolute max -0.3V to 14V. |
| 16 | PGND | power_in | Driver power ground. Connects to the source of the bottom (synchronous) N-channel MOSFET and the (-) terminal of CIN. |
| 17 | VIN | power_in | Main supply pin. A bypass capacitor should be tied between this pin and the SGND pins. Operating range 4V to 60V, absolute max -0.3V to 65V. |
| 18 | ILIM | input | Current comparator sense voltage range input. Tying this pin to SGND, FLOAT, or INTVCC sets the maximum current sense threshold to one of three different levels for the comparator (30/50/75 mV typ). Absolute max -0.3V to INTVCC. |
| 19 | TRACK/SS | input | External tracking and soft-start input. The LTC3891 regulates VFB to the smaller of 0.8V or the voltage on TRACK/SS. An internal 10μA pull-up current source is connected to this pin; a capacitor to ground sets the soft-start ramp time. Alternatively, a resistor divider on another supply allows the output to track that supply during start-up. Absolute max -0.3V to 6V. |
| 20 | FREQ | input | Frequency control pin for the internal VCO. Tie to GND for 350kHz fixed, to INTVCC for 535kHz fixed, or use a resistor from FREQ to GND (with the internal 20μA pull-up) to program frequencies between 50kHz and 900kHz. Absolute max -0.3V to INTVCC. |
| 21 | SGND (EP) | power_in | Exposed pad, small-signal ground. Must be soldered to PCB ground for rated thermal performance. Also part of the SGND group with pins 2 and 3. |
Key specifications
| Parameter | Value |
|---|---|
| Manufacturer | Analog Devices |
| Package | QFN-20-EP(3x4) |
| Category | Power Supply Chip |
| Pins | 21 |
Ordering variants
Same part, different packaging or reel option.
LTC3891EUDC#PBFLTC3891EUDC#PBFIUDC#PBFLTC3891EUDC#PBFHUDC#PBFLTC3891EUDC#PBFMPUDC#PBFLTC3891EUDC#PBFEFE#PBFLTC3891EUDC#PBFIFE#PBFLTC3891EUDC#PBFHFE#PBFLTC3891EUDC#PBFMPFE#PBF
CAD (KiCad official)
- Symbol:
LTC3891EUDC#PBF - Footprint:
Package_DFN_QFN:QFN-20-1EP_3x4mm_P0.5mm_EP1.65x2.65mm - 3D model: QFN-20-EP(3x4) (KiCad packages3D, STEP)
Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- Datasheet: Analog Devices datasheet (32 pp, sha256
21a46463d6a45e3c, retrieved 2026-08-17, tier: lcsc) - Extractor:
ds2sf(Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate. - CAD: KiCad official libraries (CC-BY-SA 4.0).