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Analog Devices Inc. LT3420EMS#PBF
- Part No.:
- LT3420EMS#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Management - Specialized
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LT3420EMS#PBF.pdf
- Description:
- IC PHOTOFLASH CAP CHARGER 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:259
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Product details
Overview
LT3420EMS#PBF from Analog Devices (formerly Linear Technology) is a high-voltage photoflash capacitor charger IC using flyback topology. It delivers controlled 1.4A peak switch current and 840mA input current to charge 220µF to 320V in 3.7s from 5V, targeting digital and film camera flash units with automatic refresh and charge-complete indication.
For engineers reviewing the LT3420EMS#PBF datasheet, LT3420EMS#PBF pinout, LT3420EMS#PBF application, or LT3420EMS#PBF equivalent, key selection criteria include its 10-lead MSOP package, adaptive off-time control for continuous-mode transformer operation, flyback voltage-based output sensing (no zener or divider), and dual-mode interface via CHARGE/DONE pins for microprocessor-controlled flash timing.
Technical Context
The LT3420EMS#PBF implements an adaptive off-time control algorithm that maintains current-limited continuous conduction mode across the full charge cycle, eliminating high inrush currents. Its output voltage regulation relies on flyback pulse monitoring at the SW pin rather than direct output feedback.
It features a master latch-driven state machine managing charging and refresh modes, with a programmable refresh timer (via CT pin capacitor) and leakage spike blanking (200ns) to prevent false triggering during switch turn-off. The internal NPN power switch has 38V DC/38V dynamic breakdown rating.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | Up to 330V - supports standard photoflash capacitors without external voltage dividers or zeners. |
| Peak Switch Current | 1.4A (typ) - sets primary-side energy transfer limit and defines transformer sizing requirements. |
| Input Voltage Range | 1.8V to 16V - enables operation from two AA cells or wide-input industrial supplies. |
| Charge Time | 3.7s to 320V @ 220µF - enables rapid flash recycling in consumer imaging systems. |
| Refresh Current | ~2mA average - sustains capacitor voltage with minimal standby power consumption. |
| Package | 10-Lead MSOP (3mm × 3mm) - compact footprint compatible with space-constrained camera modules. |
| Switch Breakdown Voltage | 38V DC / 38V dynamic - constrains maximum transformer turns ratio for safe operation. |
Pinout & Package
LT3420EMS#PBF is housed in a 10-lead plastic MSOP package with exposed pad not present (unlike DFN variant); thermal performance defined by θJA = 100°C/W on 4-layer board.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RREF (1) | Reference resistor connection | Sets internal 1V reference bias; 2kΩ to GND configures default operation. |
| VBAT (2) | Battery supply input | Primary power path to transformer primary; requires local 4.7µF ceramic bypass. |
| RFB (3) | Feedback current input | Receives current proportional to VOUT/N; enables output sensing without resistive divider. |
| VCC (4) | IC supply rail | Logic and control power; 2.5V–16V range; must be bypassed with ≥4.7µF X5R/X7R capacitor. |
| GND (5) | Signal and power ground | Common return for all analog and digital circuitry; tie directly to low-impedance ground plane. |
| SW (6) | Internal NPN switch collector | Drives transformer primary; high dv/dt node requiring minimized trace area to reduce EMI. |
| SEC (7) | Transformer secondary connection | Connects to secondary winding; polarity critical for proper flyback voltage sensing. |
| DONE (8) | Open-collector status output | Pulled low during active charging; high-Z when complete - requires external pull-up for logic interface. |
| CHARGE (9) | Enable/control input | High (≥1.5V) initiates charging; low (≤0.2V) forces shutdown; edge-triggered for forced refresh entry. |
| CT (10) | Refresh timer capacitor | External capacitor sets refresh interval (tREFRESH = CT / 2.5µA); grounding disables refresh. |
Key Features
| Feature | Design Value |
|---|---|
| Flyback voltage sensing | Eliminates need for output voltage divider or high-voltage zener, reducing BOM count and layout complexity. |
| Adaptive off-time control | Maintains continuous conduction mode across entire charge cycle, improving efficiency vs. discontinuous topologies. |
| Programmable refresh timer | Enables user-defined hold time for photoflash capacitor with ~2mA average input current - extends battery life. |
| Leakage spike blanking | 200ns one-shot disables comparator A3 during SW turn-off, preventing false trigger from transformer leakage spikes. |
| Charge-complete signaling | DONE pin provides unambiguous logic-level signal to host processor, enabling precise flash timing synchronization. |
Applications
| Digital Camera Flash Unit | Film Camera Flash Unit |
|---|---|
Use Scenario: Rapid recycling of flash capacitor between image captures in compact digital cameras powered by 2×AA batteries. IC Role / Device Role / Timing Role: High-efficiency flyback charger controlling energy transfer to 220µF/330V photoflash capacitor with DONE-synchronized firing. Use Value: Achieves 3.7s full charge from 5V while consuming only ~2mA in refresh mode - extends battery runtime without sacrificing flash readiness. | Use Scenario: Integration into legacy film camera modules requiring reliable high-voltage capacitor charging with mechanical shutter sync. IC Role / Device Role / Timing Role: Standalone photoflash charger providing regulated 320V output with CHARGE pin edge-triggered start and DONE confirmation. Use Value: Eliminates discrete zener and resistor networks traditionally used for voltage setting, reducing component count and calibration drift. |
| High-Voltage Power Supplies | Portable Medical Imaging Flash |
Use Scenario: Generating stable 300–330V rails in compact industrial sensors or portable test equipment where size and efficiency are critical. IC Role / Device Role / Timing Role: Flyback DC-DC converter core with adaptive current limiting and transformer-coupled output sensing. Use Value: Delivers >75% typical efficiency at 320V output using standard off-the-shelf transformers - avoids custom magnetics. | Use Scenario: Charging flash capacitors in handheld dermatology or dental imaging devices operating from single-cell Li-ion (3.0–4.2V). IC Role / Device Role / Timing Role: Low-input-voltage photoflash charger supporting 1.8V minimum VBAT, with automatic refresh maintaining readiness during idle periods. Use Value: Enables full 320V charge from 3.3V input in <4s while sustaining voltage with <2.5mA quiescent draw - meets portable medical battery life targets. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar photoflash capacitor charging applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3420EDD#PBF | Same electrical specs; uses 10-lead (3mm × 3mm) DFN package with exposed GND pad for improved thermal performance (θJA = 43°C/W). | Preferred for thermally constrained PCB layouts or higher ambient temperature environments (>70°C). | Select LT3420EDD#PBF when board space allows DFN footprint and thermal management is prioritized over MSOP compatibility. |
| LT3420EMS-1#PBF | Lower 1.0A peak switch current, 450mA input current, 50V SW breakdown, no leakage blanking; charges 100µF to 320V in 3.5s. | Optimized for smaller photoflash capacitors and lower-power flash systems where reduced stress on transformer and diode is required. | Choose LT3420EMS-1#PBF when designing for 100µF-class capacitors and tighter input current limits - not a drop-in replacement for LT3420EMS#PBF. |
Compared with LT3420EDD#PBF, LT3420EMS#PBF offers identical functionality in a legacy MSOP package suited for rework or existing layouts, while LT3420EMS-1#PBF trades peak current and blanking for higher SW voltage rating and lower power delivery - requiring transformer and timing component recalculation.
Availability
LT3420EMS#PBF is available at Aetrix Electronics and suitable for digital camera flash units, film camera flash modules, and high-voltage portable power supplies requiring stable component supply, long-term lifecycle support, and guaranteed authentic sourcing.
Supply support for LT3420EMS#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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors.
The LT3420 product line was designed specifically for efficient, compact photoflash capacitor charging in battery-powered imaging systems - emphasizing adaptive control, integrated sensing, and minimal external components.
FAQ
What is the minimum input voltage required for LT3420EMS#PBF to operate?
The LT3420EMS#PBF requires a minimum VBAT of 1.8V and minimum VCC of 2.5V to function. Operation below these thresholds triggers undervoltage lockout with 275mV (VBAT) and 40mV (VCC) hysteresis. These limits enable reliable startup from two fresh AA alkaline cells (~3.0V) or partially discharged lithium chemistries down to 1.8V, ensuring robustness in portable flash applications where LT3420EMS#PBF is deployed.
How does LT3420EMS#PBF regulate output voltage without a feedback divider?
The LT3420EMS#PBF regulates output voltage by sensing the flyback pulse amplitude at the SW pin during switch turn-off. This voltage is proportional to VOUT/N (where N is transformer turns ratio), and is converted to a current flowing into the RFB pin. Combined with the RREF-referenced 1V threshold, this scheme eliminates external resistive dividers or zener diodes - a core design feature of LT3420EMS#PBF that reduces component count and improves accuracy over temperature.
Can LT3420EMS#PBF be used with a 100µF photoflash capacitor?
Yes, LT3420EMS#PBF can charge a 100µF photoflash capacitor - though it is optimized for 220µF (3.7s to 320V). With appropriate transformer selection (e.g., 1:12 turns ratio) and adjusted RFB/RREF values, LT3420EMS#PBF achieves faster charge times on smaller capacitors. However, for dedicated 100µF use cases, LT3420EMS-1#PBF is better matched due to its lower 1.0A current limit and 450mA input rating - confirming LT3420EMS#PBF remains fully functional but not optimally tuned for that specific value.
What is the purpose of the CT pin on LT3420EMS#PBF?
The CT pin on LT3420EMS#PBF connects to an external capacitor that sets the refresh timer period. A 2.5µA current source charges and discharges this capacitor between 0.5V and 1.0V thresholds, generating a user-programmable delay before automatic recharge initiation. For example, a 1µF capacitor yields ~400s refresh interval. Grounding CT disables refresh entirely, making LT3420EMS#PBF rely solely on CHARGE pin control - a key flexibility feature in systems where LT3420EMS#PBF must hold voltage only on demand.
Does LT3420EMS#PBF require a special transformer or can standard parts be used?
LT3420EMS#PBF is designed to work with standard off-the-shelf flyback transformers - including TDK SRW10EPC-U01H003 (1:12) and Sumida 6375-T108 (1:12) - provided they meet three criteria: sufficient primary inductance (>24µH), low leakage inductance (to keep SW pin spikes <38V), and secondary capacitance minimized to avoid efficiency loss. No custom magnetics are required, and Linear Technology qualified multiple vendors' parts for LT3420EMS#PBF, simplifying design-in.
LT3420EMS#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Applications:
- Photoflash Capacitor Charger
- Current - Supply:
- 90µA
- Voltage - Supply:
- 2.2V ~ 16V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-MSOP
LT3420EMS#PBF FAQ
1.How can I place an order for LT3420EMS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3420EMS#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 LT3420EMS#PBF reliable?
The price and inventory of LT3420EMS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3420EMS#PBF is usually 5 days.
3.What payment methods are accepted for LT3420EMS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3420EMS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3420EMS#PBF?
LT3420EMS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3420EMS#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 LT3420EMS#PBF?
For technical support, including LT3420EMS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3420EMS#PBF requirements.
6.How does Aetrix verify that LT3420EMS#PBF is sourced from the original manufacturer or authorized distributors?
All LT3420EMS#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 LT3420EMS#PBF meets industry standards.
7.What is the process for return or replacement of LT3420EMS#PBF?
All LT3420EMS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3420EMS#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 LT3420EMS#PBF part is unused and in its original packaging.
Return procedure for LT3420EMS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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