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Analog Devices Inc. LTC3128EUFD#PBF
- Part No.:
- LTC3128EUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 20-WFQFN Exposed Pad
- Datasheet:
-
LTC3128EUFD#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 3A 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,726
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Product details
Overview
LTC3128EUFD#PBF from Analog Devices (formerly Linear Technology) is a monolithic buck-boost supercapacitor charger IC with accurate average input current limit, active charge balancing, and programmable maximum capacitor voltage. It operates from 1.73V to 5.5V input, delivers up to 3A input current, regulates output from 1.8V to 5.5V, and supports stacked supercapacitor backup power systems in servers and industrial memory retention.
For engineers reviewing the LTC3128EUFD#PBF datasheet, LTC3128EUFD#PBF pinout, LTC3128EUFD#PBF application, or LTC3128EUFD#PBF equivalent, key selection criteria include its ±2% input current accuracy, 1.2MHz fixed-frequency operation, thermal regulation at 135°C, <2µA VOUT quiescent current in Burst Mode®, and support for active balancing of unmatched supercapacitors without external resistors.
Technical Context
The LTC3128EUFD#PBF implements a proprietary continuous-mode 4-switch buck-boost topology that seamlessly transitions between buck, boost, and buck-boost modes without inductor current discontinuity or loop instability. Its dual control loops - hysteretic voltage loop and internally compensated average input current loop - enable precise regulation while minimizing chattering near VOUT setpoint.
It integrates five synchronous MOSFETs (A–F), an internal 50mΩ sense resistor, zero-current detection, thermal regulator (active reduction of IIN limit above 135°C), and dedicated balancer circuitry driving MID to equalize stacked capacitors via SW1/SW2 inductor coupling. The MAXV and PROG pins each use single-resistor programming for capacitor overvoltage protection and input current limit (0.5A–3A range).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VIN Range | 1.73V to 5.5V - supports single-cell Li-ion, USB, or wide-input industrial rails without pre-regulation. |
| VOUT Range | 1.8V to 5.5V - programmable via FB divider; enables direct charging of 2.7V/3.0V/3.3V/5V supercapacitor stacks. |
| Avg Input Current Limit | 0.5A to 3.0A ±2% - set by single RPROG; critical for battery-limited or USB-powered backup systems. |
| Max Cap Voltage Limit | 1.8V to 3.0V per capacitor - set by single RMAXV; prevents overvoltage failure in series-connected supercaps. |
| Switching Frequency | 1.2MHz typical - enables compact 3.3µH inductor and low-profile ceramic output capacitors. |
| Quiescent Current (VOUT) | <2µA in Burst Mode® - extends hold-up time during standby in memory backup applications. |
| Thermal Regulation Threshold | 135°C (typ) - dynamically reduces IIN limit to prevent thermal shutdown during high-current charging. |
Pinout & Package
The LTC3128EUFD#PBF is housed in a thermally enhanced 20-lead 4mm × 5mm × 0.75mm plastic QFN package with exposed pad (Pin 21) soldered to PCB ground for optimal thermal performance (θJA = 43°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW1 (Pins 1, 19) | High-side switch node (MOSFETs A/B) | Connects to one end of power inductor; carries full switching current in all operating modes. |
| RSENP (Pin 2) | Power output of internal sense resistor | Supplies system loads downstream of sense resistor; requires local 10µF ceramic bypass. |
| RSENS (Pin 3) | Sense resistor signal input | Low-impedance connection point for accurate input current measurement; must be short/wide trace to RSENP. |
| RUN (Pin 4) | Logic-controlled enable/shutdown | Active-high (≥1.2V); pulls internal switches off when ≤0.3V; supports VIN/VOUT-level logic drive. |
| PROG (Pin 5) | Average input current limit programming | Resistor-to-GND sets IIN limit (RPROG = 11kΩ/A); includes capacitor for noise filtering. |
| VIN (Pin 7) | Main input supply and VCC source | High-current path for input power; requires local 10µF ceramic bypass to GND. |
| PFO (Pin 8) | Open-drain power-fail output | Sinks current when monitored supply falls below PFI threshold; used for system brownout warning. |
| PFI (Pin 9) | Power-fail monitor input | Accepts resistor divider from monitored rail; internal 0.58V reference enables programmable UVLO. |
| MAXV (Pin 10) | Maximum capacitor voltage programming | Resistor-to-GND sets per-capacitor overvoltage limit (RMAXV = 50kΩ/V); disables balancer if grounded. |
| FB (Pin 11) | Output voltage feedback | Connects to resistor divider; 0.58V internal reference enables 1.8V–5.5V VOUT programming. |
| PGOOD (Pin 12) | Open-drain power-good indicator | Pulls low when VOUT drops below 96.75% of programmed value; provides system power-status signaling. |
| MID (Pin 13) | Active balancer midpoint sensing | Connected to junction of stacked capacitors; enables charge redistribution when imbalance exceeds 60mV. |
| VOUTS (Pin 14) | Output voltage sense input | High-impedance Kelvin sense point; minimizes IR drop error in high-current supercapacitor charging. |
| VOUTP (Pins 15, 16) | Synchronous rectifier output | Primary output node; connects to bulk output capacitor; handles full load current with low RDS(ON). |
| SW2 (Pins 17, 18) | Low-side switch node (MOSFETs C/D) | Connects to other end of power inductor; complements SW1 in buck-boost energy transfer. |
| GND (Exposed Pad Pin 21) | Power and signal ground | Must be soldered to large PCB ground plane for thermal dissipation and noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| Accurate average input current limit | ±2% tolerance over temperature; enables reliable USB/energy-harvesting input current budgeting. |
| Active charge balancing | 60mV imbalance threshold; moves charge bidirectionally via inductor without lossy resistors. |
| Programmable per-capacitor overvoltage protection | 1.8V–3.0V range via single resistor; prevents premature degradation of series-connected supercaps. |
| Thermal regulation | Reduces IIN limit progressively above 135°C to avoid shutdown during sustained high-power charging. |
| Burst Mode® operation | <2µA VOUT quiescent current; maximizes hold-up time in memory backup during long idle periods. |
Applications
| Server Backup Power | Industrial Memory Retention |
|---|---|
Use Scenario: Maintaining DRAM/NVRAM state during AC mains failure in rack-mounted servers. IC Role / Device Role / Timing Role: Buck-boost supercapacitor charger providing regulated 3.3V/5V hold-up power with active balancing of 2×2.7V supercaps. Use Value: Enables >10-second data save window using compact 1F stacked supercapacitors without manual balancing resistors. | Use Scenario: Preserving configuration and real-time clock data in PLCs and HMIs during brownouts. IC Role / Device Role / Timing Role: Supercapacitor charger with programmable 2.5V per-cell limit and thermal regulation for extended field life. Use Value: Eliminates battery replacement cycles and guarantees >5-year backup reliability under industrial temperature cycling. |
| RAID Controller Hold-Up | RF System Power Fail Recovery |
Use Scenario: Preventing write-cache corruption in enterprise storage arrays during unexpected power loss. IC Role / Device Role / Timing Role: Fast-charging controller for 4.2V supercapacitor stack with 3A input current limit and PFO/PFI monitoring. Use Value: Achieves full capacitor charge in <15 seconds (1F, 20mΩ ESR), enabling deterministic flush-and-shutdown sequences. | Use Scenario: Supporting graceful RF transceiver re-synchronization after brief grid interruptions in telecom base stations. IC Role / Device Role / Timing Role: Low-quiescent charger with PGOOD signaling and 1.73V minimum VIN for ultra-low-voltage operation. Use Value: Delivers uninterrupted 2.5V bias to RF front-end during 100ms–500ms outages using minimal board space. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar supercapacitor charger applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3129EUFD#PBF | Higher 4A max input current; integrated 100mΩ sense resistor; no RSENS/RSENP separation. | Optimized for higher-power backup; lacks separate RSENP for system load sharing. | Select LTC3129EUFD#PBF when >3A input current or simplified layout is required; not pin-compatible. |
| MAX17599ATP+T | Fixed 2.5A input limit; no active balancing; only single-capacitor support; 2.5V–5.5V VIN range. | Lower-cost solution for non-stacked supercapacitor applications; no MID or MAXV functionality. | Select MAX17599ATP+T for cost-sensitive single-capacitor designs where balancing is unnecessary. |
Compared with LTC3128EUFD#PBF, LTC3129EUFD#PBF offers higher current but removes system load integration flexibility, while MAX17599ATP+T simplifies design at the expense of stacking and balancing capability - making LTC3128EUFD#PBF the optimal choice for precision-balanced dual-supercapacitor backup systems.
Availability
LTC3128EUFD#PBF is available at Aetrix Electronics and suitable for server backup power, industrial memory retention, and RAID controller hold-up requiring stable component supply across extended product lifecycles.
Supply support for LTC3128EUFD#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, formed through the acquisition of Linear Technology in 2017.
The LTC3128EUFD#PBF belongs to ADI's Power by Linear™ supercapacitor charger family, designed specifically for safe, efficient, and intelligent charging of stacked supercapacitors in mission-critical backup power systems.
FAQ
What is the maximum input current limit achievable with LTC3128EUFD#PBF?
The LTC3128EUFD#PBF supports a programmable average input current limit from 0.5A to 3.0A with ±2% accuracy. This is set using a single resistor (RPROG) from the PROG pin to GND, calculated as RPROG(kΩ) = 11 / ILIMIT(A). At 3.0A, RPROG = 3.67kΩ; the device maintains this accuracy across –40°C to 125°C junction temperature.
How does LTC3128EUFD#PBF perform active charge balancing for stacked supercapacitors?
The LTC3128EUFD#PBF uses its MID pin to sense the midpoint voltage of two series-connected supercapacitors. When imbalance exceeds 60mV, it modulates internal switches C and D via the SW1–SW2 inductor to move charge bidirectionally - boosting from bottom to top or bucking from top to bottom - until voltages equalize. No external balancing components are needed.
Can LTC3128EUFD#PBF charge a single supercapacitor, and how is maximum voltage set in that case?
Yes, LTC3128EUFD#PBF can charge a single supercapacitor. In this configuration, tie the MAXV pin to GND to disable both the per-capacitor overvoltage comparator and active balancer. The output voltage is then regulated solely via the FB pin using a resistor divider, with the internal 0.58V reference setting VOUT = 0.58 × (1 + R2/R1).
What thermal management features does LTC3128EUFD#PBF include to prevent overheating during high-current charging?
The LTC3128EUFD#PBF incorporates three thermal protections: (1) thermal shutdown at ~165°C, (2) thermal regulation starting at ~135°C (progressively reducing IIN limit down to ~30%), and (3) mandatory exposed-pad soldering to PCB ground (θJA = 43°C/W). These ensure reliable 3A charging even in compact, sealed enclosures.
Does LTC3128EUFD#PBF support power-fail detection and system-level signaling?
Yes, LTC3128EUFD#PBF includes dedicated PFI (power-fail input) and PFO (power-fail output) pins. An external resistor divider on PFI sets the undervoltage threshold relative to the internal 0.58V reference. When the monitored rail falls below this threshold, PFO pulls low - providing immediate system-level brownout warning without additional comparators.
LTC3128EUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck-Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 1.73V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 1.8V
- Voltage - Output (Max):
- 5.5V
- Current - Output:
- 3A
- Frequency - Switching:
- 1.2MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QFN (4x5)
LTC3128EUFD#PBF FAQ
1.How can I place an order for LTC3128EUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3128EUFD#PBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LTC3128EUFD#PBF reliable?
The price and inventory of LTC3128EUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3128EUFD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3128EUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3128EUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3128EUFD#PBF?
LTC3128EUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3128EUFD#PBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LTC3128EUFD#PBF?
For technical support, including LTC3128EUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3128EUFD#PBF requirements.
6.How does Aetrix verify that LTC3128EUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3128EUFD#PBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LTC3128EUFD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3128EUFD#PBF?
All LTC3128EUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3128EUFD#PBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LTC3128EUFD#PBF part is unused and in its original packaging.
Return procedure for LTC3128EUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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