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Analog Devices Inc. LTC3128EFE#PBF
- Part No.:
- LTC3128EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 24-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LTC3128EFE#PBF.pdf
- Description:
- IC REG BUCK BOOST ADJ 3A 24TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:164
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Product details
Overview
LTC3128EFE#PBF from Analog Devices (formerly Linear Technology) is a monolithic buck-boost supercapacitor charger IC with accurate average input current limiting, active charge balancing, and programmable maximum capacitor voltage. It operates across 1.73V–5.5V input and 1.8V–5.5V output ranges, delivers up to 3A input current, and supports stacked supercapacitor backup power systems in servers and industrial equipment.
For engineers reviewing the LTC3128EFE#PBF datasheet, LTC3128EFE#PBF pinout, LTC3128EFE#PBF application, or LTC3128EFE#PBF equivalent, key selection criteria include its ±2% accurate input current limit, 0.58V feedback reference, 1.2MHz fixed switching frequency, thermal regulation at 135°C, and support for active balancing of unmatched capacitors without external resistors.
Technical Context
The LTC3128EFE#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 regulation and average input current PWM-enable precise VOUT regulation while maintaining tight IIN control over temperature and line variations.
It integrates five internal MOSFETs (A–F), a 50mΩ internal sense resistor, zero-current detection, thermal regulation (135°C activation), and a dedicated active balancer using SW1/SW2 and MID to shuttle charge between stacked capacitors at programmable thresholds (±60mV enable hysteresis, ±400mA peak balancer current).
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; 0.58V reference enables stable regulation for 2×2.7V or 2×3.0V supercap stacks. |
| Avg Input Current Limit | 0.5A to 3.0A - set by single RPROG resistor; ±2% accuracy ensures predictable charge time and thermal budgeting. |
| Switching Frequency | 1.2MHz (typ) - enables compact 3.3µH inductor and low-profile ceramic output capacitors. |
| Quiescent Current (Sleep) | <2µA from VOUT - extends battery/supercap hold-up time in memory backup applications. |
| Max Capacitor Voltage | 1.8V to 3.0V per cell - set by single RMAXV resistor; ±6% tolerance accommodates capacitor aging and ESR drift. |
| Active Balancer Threshold | ±60mV imbalance - triggers automatic charge redistribution before overvoltage damage occurs. |
Pinout & Package
Package: 24-Lead Plastic TSSOP (FE package), 0.75mm nominal height, exposed thermal pad (Pin 25) requiring PCB ground soldering for θJA = 38°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW1 (Pins 1, 4) | High-side switch node (MOSFETs A/B) | Connects to one end of power inductor; carries full charging current in buck/boost transitions. |
| RSENP (Pin 5) | Power output of internal sense resistor | Supplies system loads downstream of sense path; requires ≥10µF local ceramic decoupling. |
| RSENS (Pin 6) | Sense resistor signal input | Low-impedance connection point for accurate input current measurement; must be short/wide trace to RSENP. |
| RUN (Pin 7) | Logic-controlled enable/shutdown | 1.2V threshold enables operation; 0.3V threshold forces shutdown with <1µA IQ and output disconnect. |
| PROG (Pin 8) | Average input current limit programming | Resistor-to-GND sets IIN limit (RPROG = 11kΩ/A); capacitor adds noise filtering and loop stability. |
| VIN (Pin 11) | Main input supply and VCC source | Provides bias for internal circuitry and high-current path into sense resistor; requires ≥10µF local ceramic cap. |
| PFO (Pin 13) | Open-drain power-fail indicator output | Sinks current when monitored supply falls below PFI threshold; compatible with 3.3V/5V logic interfaces. |
| PFI (Pin 14) | Power-fail monitor input | Accepts resistor divider tap; internal 0.58V reference enables precise brown-out detection with hysteresis. |
| MAXV (Pin 15) | Maximum per-capacitor voltage programming | Resistor-to-GND sets upper voltage limit (RMAXV = 50kΩ/V); disables balancer if tied to GND. |
| FB (Pin 16) | Output voltage feedback input | 0.58V reference enables 1.8V–5.5V VOUT programming; high-impedance input minimizes divider error. |
| PGOOD (Pin 17) | Open-drain power-good indicator | Pulls low when VOUT drops below 96.75% of programmed value; provides system-level power status signaling. |
| MID (Pin 18) | Stack midpoint sensing and balancer interface | Must connect to junction of two series capacitors; enables active balancing only when |VOUT/2 − VMID| > 60mV. |
| VOUTS (Pin 19) | Output voltage sense input | Direct Kelvin connection point to VOUT capacitor; reduces regulation error from PCB trace resistance. |
| VOUTP (Pins 20, 21) | Synchronous rectifier output | High-current output node for filter capacitor; connects to GND via low-ESR ceramic capacitor bank. |
| SW2 (Pins 23, 24) | Low-side switch node (MOSFETs C/D) | Connects to other end of power inductor; complements SW1 in 4-switch operation. |
| GND (Pins 2, 3, 12, 25) | Signal and power ground | Exposed thermal pad (Pin 25) must be soldered to PCB ground plane for thermal performance and EMI control. |
Key Features
| Feature | Design Value |
|---|---|
| Accurate average input current limit | ±2% tolerance over –40°C to 125°C enables repeatable charge time and thermal design without calibration. |
| Active charge balancing | Eliminates need for lossy passive balancing resistors; redistributes charge at up to 400mA peak current to extend supercap lifetime. |
| Programmable per-capacitor overvoltage protection | Single-resistor MAXV setting prevents individual cell overvoltage in stacked configurations, critical for long-term reliability. |
| Thermal regulation | Reduces programmed input current limit starting at 135°C die temperature, preventing thermal runaway during high-current charging. |
| Burst Mode® operation | Delivers <2µA quiescent current from VOUT when charged, minimizing self-discharge in backup power hold-up applications. |
Applications
| Server Backup Power | Memory Data Retention |
|---|---|
Use Scenario: Maintaining volatile memory (e.g., DDR SDRAM, SRAM) during AC mains failure in rack-mounted servers. IC Role / Device Role / Timing Role: Buck-boost supercapacitor charger providing regulated 4.2V stack output with active balancing to sustain memory voltage for 10–60 seconds. Use Value: Enables deterministic hold-up time via 3A programmable input current and <2µA sleep IQ, eliminating battery maintenance and leakage concerns. | Use Scenario: Preserving configuration data in industrial PLCs and telecom base stations during brief power interruptions. IC Role / Device Role / Timing Role: Charging and balancing dual 2.7V supercapacitors to deliver stable 5.4V backup rail for real-time clock and nonvolatile registers. Use Value: Prevents data corruption by enforcing ≤3.0V per cell via MAXV programming and active balancing, even with mismatched capacitor ESR or capacitance. |
| RAID Controller Protection | RF System Power Integrity |
Use Scenario: Safeguarding write-cache buffers in enterprise storage arrays against sudden power loss. IC Role / Device Role / Timing Role: Delivering fast, controlled charge to high-capacitance (>1F) supercap banks with precise 3A input current limiting and thermal regulation. Use Value: Guarantees consistent charge time across temperature via ±2% IIN accuracy and avoids thermal derating through 135°C thermal regulation. | Use Scenario: Providing clean, uninterrupted bias to RF front-end modules (LNA, PA) during transient grid disturbances. IC Role / Device Role / Timing Role: Regulating 3.3V output from variable 2.4–4.2V input sources while suppressing ripple with 1.2MHz switching and synchronous rectification. Use Value: Minimizes RF noise injection via fixed-frequency operation and low-ESR ceramic output caps, preserving signal integrity in sensitive analog paths. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar supercapacitor charger applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3129EFE#PBF | Higher 4A max input current; integrated 100mΩ sense resistor; no RSENP/RSENS pins. | Optimized for higher-power backup systems; lacks separate RSENP path for system load sharing. | Select LTC3129EFE#PBF when >3A charging is required and no external load sharing on RSENP is needed. |
| MAX17599ATP+T | Fixed 2.5A input current limit; no active balancing; uses external sense resistor; 2.2MHz switching. | Suitable for single-capacitor backup; lacks per-cell voltage monitoring and charge redistribution capability. | Select MAX17599ATP+T for cost-sensitive, non-stacked supercap applications where balancing is unnecessary. |
Compared with LTC3128EFE#PBF, LTC3129EFE#PBF offers higher current but removes RSENP flexibility, while MAX17599ATP+T simplifies design for single-capacitor use but omits critical balancing and programmable per-cell overvoltage protection.
Availability
LTC3128EFE#PBF is available at Aetrix Electronics and suitable for server backup power, memory retention, and RAID controller protection requiring stable component supply and long-lifecycle availability.
Supply support for LTC3128EFE#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 acquired Linear Technology in 2017 and maintains full technical and manufacturing continuity for all Linear power products.
The LTC3128 belongs to Linear's high-efficiency supercapacitor charger product line, designed specifically for reliable, programmable backup power in mission-critical computing and industrial systems.
FAQ
What is the operating temperature range for the LTC3128EFE#PBF?
The LTC3128EFE#PBF is specified for operation from –40°C to +125°C junction temperature. This grade (E-grade) is guaranteed over 0°C to 85°C junction temperature and assured by design across the full –40°C to 125°C range, making it suitable for industrial and automotive under-hood environments where thermal robustness is essential. The FE package's θJA of 38°C/W requires proper PCB thermal design to maintain reliability at maximum load.
How does the LTC3128EFE#PBF implement active charge balancing?
The LTC3128EFE#PBF implements active charge balancing by using its internal SW1 and SW2 switches and the MID pin to form a bidirectional buck-boost converter between stacked capacitors. When |VOUT/2 − VMID| exceeds ±60mV, the balancer activates, modulating switches C/F or D/F to transfer charge at up to 400mA peak current until balance is restored. This eliminates reliance on inefficient passive resistors and preserves energy in the stack.
Can the LTC3128EFE#PBF charge a single supercapacitor?
Yes, the LTC3128EFE#PBF can charge a single supercapacitor. In this configuration, tie the MAXV pin to GND to disable both the per-cell overvoltage comparator and the active balancer, and program the output voltage via the FB divider. The MID pin must also be tied to GND. Output regulation remains fully functional, with VOUT adjustable from 1.8V to 5.5V using the 0.58V internal reference.
What is the purpose of the RSENP and RSENS pins on the LTC3128EFE#PBF?
The RSENP and RSENS pins on the LTC3128EFE#PBF provide a Kelvin-sense configuration for accurate input current measurement. RSENP serves as the power output of the internal 50mΩ sense resistor and supplies external system loads, while RSENS is the low-impedance signal return. This separation allows the LTC3128EFE#PBF to regulate average input current precisely-even when additional loads draw current from RSENP-by measuring only the current flowing through the sense resistor.
Does the LTC3128EFE#PBF support programmable undervoltage lockout (UVLO)?
No, the LTC3128EFE#PBF features a fixed internal undervoltage lockout threshold of 1.60V (typical), with turn-on occurring at 1.73V. UVLO is not user-programmable; however, the PFI/PFO pins provide a fully programmable power-fail detection function using an external resistor divider, enabling custom brown-out thresholds independent of VIN UVLO behavior.
LTC3128EFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 24-TSSOP (0.173", 4.40mm Width) 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:
- 24-TSSOP
LTC3128EFE#PBF FAQ
1.How can I place an order for LTC3128EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3128EFE#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 LTC3128EFE#PBF reliable?
The price and inventory of LTC3128EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3128EFE#PBF is usually 5 days.
3.What payment methods are accepted for LTC3128EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3128EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3128EFE#PBF?
LTC3128EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3128EFE#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 LTC3128EFE#PBF?
For technical support, including LTC3128EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3128EFE#PBF requirements.
6.How does Aetrix verify that LTC3128EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3128EFE#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 LTC3128EFE#PBF meets industry standards.
7.What is the process for return or replacement of LTC3128EFE#PBF?
All LTC3128EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3128EFE#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 LTC3128EFE#PBF part is unused and in its original packaging.
Return procedure for LTC3128EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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