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Analog Devices Inc. LTC3556EUFD#PBF
- Part No.:
- LTC3556EUFD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Management - Specialized
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LTC3556EUFD#PBF.pdf
- Description:
- IC USB POWER MANAGE 28QFN
- Quantity:
- Payment:
- Shipping:
Inventory:237
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Product details
Overview
LTC3556EUFD#PBF from Analog Devices (formerly Linear Technology) is a highly integrated USB power management and battery charging IC for single-cell Li-Ion/Polymer systems. It integrates a switching PowerPath manager with automatic load prioritization, full-featured battery charger (1.5A max), internal 180mΩ ideal diode, and three synchronous regulators: two 400mA bucks and one 1A buck-boost - all operating at 2.25MHz. It enables instant-on operation with discharged batteries in handheld USB-powered devices like GPS units and portable media players.
For engineers reviewing the LTC3556EUFD#PBF datasheet, LTC3556EUFD#PBF pinout, LTC3556EUFD#PBF application, or LTC3556EUFD#PBF equivalent, key selection considerations include USB current limit programmability (100/500/1000mA), I²C-controlled dynamic voltage scaling on dual buck outputs, Bat-Track™ adaptive output control, thermal regulation, and NTC-based battery temperature monitoring.
Technical Context
The LTC3556EUFD#PBF implements a high-efficiency switching PowerPath architecture with Bat-Track™ adaptive output control that dynamically adjusts VOUT to track battery voltage plus a small offset (e.g., BAT + 0.3V), minimizing power loss across the ideal diode path. Its input stage supports USB-compliant current limiting (100mA/500mA/1A) and includes undervoltage lockout (VBUS UVLO = 3.95V rising).
All three DC/DCs operate at a fixed 2.25MHz switching frequency, enabling compact external components. Buck regulators 1 and 2 support I²C-programmable output voltages (0.8V–3.6V) via 16-step servo feedback (FB1/FB2), while buck-boost regulator 3 provides 2.5V–3.3V/1A output (VOUT3) with independent FB3/VC3 compensation nodes and forward/reverse burst current limiting.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | VBUS: 4.35V–5.5V (USB-compliant); VIN1/VIN2/VIN3: 2.7V–5.5V |
| Battery Charger | Li-Ion/Polymer, 4.165V–4.235V float voltage, 1.5A max CC current, C/10 termination |
| PowerPath Efficiency | Delivers >95% of 2.5W USB power to system load; PMOS RDS(ON) = 0.18Ω, NMOS = 0.30Ω |
| Dual Buck Outputs | Each delivers up to 400mA at 0.8V–3.6V; I²C-programmable, 2.25MHz, 25mV step resolution |
| Buck-Boost Output | 1A at 2.5V–3.3V (VOUT3); 2.25MHz PWM/Burst mode; ILIMF3 = 2.5A forward limit |
| I²C Interface | Standard-mode (400kHz), address 0x11 (0001001[0]), DVCC-supplied (1.6V–5.5V) |
| Quiescent Current | 20µA per buck regulator (no-load), <30µA from battery, 0.31mA USB suspend mode |
Pinout & Package
The LTC3556EUFD#PBF is housed in a 28-pin, 4mm × 5mm × 0.75mm low-profile QFN package (UFD) with exposed pad (Pin 29) soldered to PCB ground for thermal performance. Pin functions are validated per Linear Technology's official datasheet (3556fa Rev. D).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| LDO3V3 (1) | Always-on 3.3V LDO output | Supplies RTC/watchdog logic; requires 1µF bypass; disable by tying to VOUT |
| CLPROG (2) | USB current limit programming/monitoring | Sets VBUS current limit (100/500/1000mA) via resistor; servo voltage = 1.188V |
| NTC (3) | Battery thermistor interface | Monitors battery temperature; enables hot/cold charge pause; requires bias resistor + thermistor |
| SW1 (4) | Buck 1 switch node | Connects to external inductor; handles high-frequency switching current |
| VIN1 (5) | Buck 1 input supply | Typically connected to VOUT; requires 1µF MLCC decoupling |
| FB1 (6) | Buck 1 feedback input | I²C-programmable 16-level servo (0.405V–0.820V); sets VOUT1 = 0.8V–3.6V |
| FB3 (7) | Buck-boost 3 feedback input | I²C-programmable 16-level servo; sets VOUT3 = 2.5V–3.3V |
| VC3 (8) | Buck-boost 3 error amplifier output | Compensation node for external Type I/III network; stabilizes VOUT3 loop |
| SWAB3 (9) | Buck-boost 3 switch A/B node | Connects to one end of external inductor; drives internal PMOS/NMOS pair A/B |
| DVCC (10) | I²C logic supply | Powers SDA/SCL interface; range 1.6V–5.5V; UVLO = 1.0V |
| VIN3 (11) | Buck-boost 3 input supply | Typically connected to VOUT; requires ≥1µF MLCC decoupling |
| VOUT3 (12) | Buck-boost 3 regulated output | Delivers 1A at 2.5V–3.3V; used for HDD/IO or core logic requiring higher voltage |
| SCL (13) | I²C clock input | Open-drain compatible; logic levels referenced to DVCC |
| SWCD3 (14) | Buck-boost 3 switch C/D node | Connects to other end of external inductor; drives internal NMOS/PMOS pair C/D |
| PGOODALL (15) | Global power-good indicator | Open-drain output asserting when all enabled regulators settle within tolerance |
| SDA (16) | I²C data input/output | Open-drain compatible; logic levels referenced to DVCC; supports 400kHz |
| FB2 (17) | Buck 2 feedback input | Fixed 0.8V reference; sets VOUT2 = 0.8V–3.6V via external resistor divider |
| VIN2 (18) | Buck 2 input supply | Typically connected to VOUT; requires 1µF MLCC decoupling |
| SW2 (19) | Buck 2 switch node | Connects to external inductor; handles high-frequency switching current |
| PROG (20) | Battery charge current program/monitor | 1V servo in CC mode; programs ICHG via resistor (e.g., 1kΩ → 1A); reports actual current |
| CHRG (21) | Charge status open-drain output | 35kHz modulated signal indicating charge state (charging/not charging/temp fault/bad battery) |
| GATE (22) | External ideal diode FET gate driver | Analog output driving external P-MOSFET to parallel internal ideal diode; improves efficiency under heavy load |
| BAT (23) | Single-cell Li-Ion battery terminal | Charged from VOUT or powers VOUT via ideal diode; supports NTC monitoring |
| VOUT (24) | PowerPath output / system rail | Switching output (BAT+0.3V typical); supplies VIN1/VIN2/VIN3/LDO3V3; tracks battery |
| VBUS (25) | USB input supply | Accepts 4.35V–5.5V; includes 7V transient rating; current-limited per CLPROG setting |
| SEQ (26) | Power-up sequencing control | Active-low enable; controls startup order of regulators and ENALL behavior |
| ENALL (27) | Global enable input | Logic-high active; initiates power-up sequence; pull-down resistance = 4.5MΩ |
| SW (28) | PowerPath main switch node | Internal switching node between VBUS and VOUT; connects to external inductor |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive Bat-Track™ VOUT control | Maintains minimal dropout across ideal diode (VOUT ≈ BAT + 0.3V), reducing heat and extending battery runtime |
| Triple synchronous DC/DC regulation | Two 400mA bucks + one 1A buck-boost, all at 2.25MHz - enables <1mm height designs with ceramic inductors |
| I²C programmability | Enables dynamic voltage scaling on both buck outputs and buck-boost output, supporting processor DVFS and multi-rail SoC power schemes |
| Thermal regulation & safety timers | Includes junction temperature limiting (110°C), 4-hour safety timer, and bad-battery detection (0.5hr timeout below 2.85V) |
| Instant-on with discharged battery | Delivers regulated VOUT even when BAT is <2.7V, enabling immediate system boot without waiting for charge |
| NTC-based battery temperature monitoring | Pauses charging outside 0°C–45°C (configurable via VCOLD/VHOT thresholds), meeting JEITA compliance requirements |
Applications
| HDD-Based MP3 Players | GPS Navigation Devices |
|---|---|
Use Scenario: Portable audio player with mechanical hard disk drive requiring stable 3.3V/1A for HDD spin-up and 1.2V/400mA for ARM core. IC Role / Device Role / Timing Role: LTC3556EUFD#PBF acts as primary power manager: VOUT powers HDD motor via buck-boost (VOUT3), buck1 supplies core voltage, buck2 powers memory, and LDO3V3 runs RTC. Use Value: Delivers 1A at 3.3V from USB input with >90% efficiency, enabling fast HDD access without thermal throttling in compact enclosures. |
Use Scenario: Battery-powered automotive GPS unit needing reliable cold-start operation and USB recharging. IC Role / Device Role / Timing Role: LTC3556EUFD#PBF manages dual power sources (VBUS and Li-Ion), provides instant-on VOUT from dead battery, and regulates 3.3V for GPS module and 1.8V for baseband processor. Use Value: Bat-Track™ ensures consistent VOUT during battery discharge; NTC monitoring prevents charging below 0°C - critical for automotive winter use. |
| USB-Powered PDAs | Portable Media Players (PMPs) |
Use Scenario: Handheld PDA with touchscreen, Wi-Fi, and SD card requiring multiple voltage rails and USB host-mode charging. IC Role / Device Role / Timing Role: LTC3556EUFD#PBF serves as central PMIC: PowerPath manages USB/adapter input priority, battery charger handles 1A CC/CV, and dual bucks power display controller (2.8V) and RF section (1.2V). Use Value: Programmable USB current limit (100/500mA) allows compliance with USB spec while maximizing charge rate when host permits. |
Use Scenario: High-resolution video-capable PMP needing efficient multi-rail power with low quiescent current during standby. IC Role / Device Role / Timing Role: LTC3556EUFD#PBF supplies 3.3V/25mA to memory, 1.6V/400mA to video decoder, and 2.5V/400mA to display driver - all synchronized via I²C and ENALL sequencing. Use Value: 20µA no-load IQ per buck and <30µA battery drain extend standby time beyond 7 days on a 1000mAh cell. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multi-rail USB power management applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX8677AETG+ | Single 1.2A buck + linear charger only; no buck-boost; no I²C programmability; 3mm × 3mm TQFN-20 | Lacks triple-regulator flexibility and dynamic voltage scaling; suitable only for simpler dual-rail systems | Select MAX8677AETG+ only if design requires lower BOM count, smaller footprint, and does not need buck-boost or I²C control. |
| BQ24195RGER | Dedicated USB charger + single 1.2A buck; no second buck or buck-boost; integrated OTG boost; I²C interface present | Optimized for charging-first use cases; lacks independent dual-buck regulation for complex SoCs | Choose BQ24195RGER when USB OTG capability and cost-sensitive single-buck designs outweigh need for triple-output flexibility. |
Compared with MAX8677AETG+ and BQ24195RGER, the LTC3556EUFD#PBF uniquely combines triple synchronous regulation, Bat-Track™ adaptive VOUT, and full I²C programmability - making it the only option capable of powering multi-voltage SoCs (e.g., ARM + GPU + memory) from USB while maintaining thermal headroom and battery longevity.
Availability
LTC3556EUFD#PBF is available at Aetrix Electronics and suitable for HDD-based MP3 players, GPS navigation devices, USB-powered PDAs, portable media players, and other USB-connected handheld products requiring stable component supply, long battery life, and robust thermal management.
Supply support for LTC3556EUFD#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 its legacy of high-performance analog and power management ICs targeting precision, efficiency, and integration in demanding applications.
The LTC3556EUFD#PBF belongs to Linear's PowerPath® family of USB-aware power managers, designed specifically for space-constrained, battery-backed portable electronics requiring seamless source arbitration, intelligent charging, and multi-rail DC/DC conversion.
FAQ
What is the maximum battery charge current supported by the LTC3556EUFD#PBF?
The LTC3556EUFD#PBF supports a maximum constant-current battery charge current of 1.5A, programmable via the PROG pin using an external resistor (e.g., 1kΩ yields ~1A; 500Ω yields ~1.5A). The charger implements CC/CV regulation with 4.165V–4.235V float voltage accuracy and C/10 termination detection. Thermal regulation limits current if junction temperature exceeds 110°C.
How does the LTC3556EUFD#PBF handle power source arbitration between USB and battery?
The LTC3556EUFD#PBF uses a high-efficiency switching PowerPath manager with automatic load prioritization. When VBUS is present, it powers the system load directly while simultaneously charging the battery. If VBUS is removed or insufficient, the internal 180mΩ ideal diode seamlessly transfers load to the battery. Bat-Track™ ensures VOUT tracks BAT + 0.3V, minimizing conduction loss during battery-only operation.
Can the LTC3556EUFD#PBF generate three independent output voltages simultaneously?
Yes - the LTC3556EUFD#PBF independently regulates three outputs: VOUT1 (buck, 0.8V–3.6V/400mA), VOUT2 (buck, 0.8V–3.6V/400mA), and VOUT3 (buck-boost, 2.5V–3.3V/1A). VOUT1 and VOUT3 are I²C-programmable across 16 voltage steps; VOUT2 uses a fixed 0.8V FB reference with external resistor divider. All operate at 2.25MHz and support dynamic voltage scaling.
What is the role of the CLPROG pin on the LTC3556EUFD#PBF?
The CLPROG pin on the LTC3556EUFD#PBF programs and monitors the USB input current limit. A resistor from CLPROG to GND sets the maximum VBUS draw (100mA/500mA/1A). During operation, a fraction of VBUS current is mirrored to CLPROG; the PowerPath controller regulates until CLPROG reaches 1.188V. An RC filter is required for stable current limiting and accurate monitoring.
Does the LTC3556EUFD#PBF support battery temperature monitoring?
Yes - the LTC3556EUFD#PBF includes dedicated NTC pin circuitry for battery thermistor interfacing. It monitors battery temperature continuously and pauses charging if the battery is too hot (>45°C) or too cold (<0°C), based on user-configurable VCOLD and VHOT thresholds. This meets JEITA-compliant charging requirements and protects Li-Ion cell integrity.
LTC3556EUFD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Applications:
- Handheld/Mobile Devices
- Current - Supply:
- -
- Voltage - Supply:
- 4.35V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QFN (4x5)
LTC3556EUFD#PBF FAQ
1.How can I place an order for LTC3556EUFD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC3556EUFD#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 LTC3556EUFD#PBF reliable?
The price and inventory of LTC3556EUFD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC3556EUFD#PBF is usually 5 days.
3.What payment methods are accepted for LTC3556EUFD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC3556EUFD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC3556EUFD#PBF?
LTC3556EUFD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC3556EUFD#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 LTC3556EUFD#PBF?
For technical support, including LTC3556EUFD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC3556EUFD#PBF requirements.
6.How does Aetrix verify that LTC3556EUFD#PBF is sourced from the original manufacturer or authorized distributors?
All LTC3556EUFD#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 LTC3556EUFD#PBF meets industry standards.
7.What is the process for return or replacement of LTC3556EUFD#PBF?
All LTC3556EUFD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC3556EUFD#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 LTC3556EUFD#PBF part is unused and in its original packaging.
Return procedure for LTC3556EUFD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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