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Analog Devices Inc. LT3420EMS-1#PBF
- Part No.:
- LT3420EMS-1#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Management - Specialized
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LT3420EMS-1#PBF.pdf
- Description:
- IC PHOTOFLASH CAP CHARGER 10MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,884
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Product details
Overview
LT3420EMS-1#PBF from Analog Devices (formerly Linear Technology) is a high-voltage photoflash capacitor charger IC using flyback topology. It delivers 1.0A peak switch current and 450mA controlled input current to charge a 100µF/320V capacitor from 5V in 3.5 seconds, targeting digital and film camera flash units with automatic refresh and charge-complete indication.
For engineers reviewing the LT3420EMS-1#PBF datasheet, LT3420EMS-1#PBF pinout, LT3420EMS-1#PBF application, or LT3420EMS-1#PBF equivalent, key selection criteria include its 10-pin MSOP package, 50V SW pin breakdown rating, adaptive off-time control for continuous-mode operation, and integrated output voltage sensing without external divider or zener diode.
Technical Context
The LT3420EMS-1#PBF implements adaptive off-time control to maintain current-limited continuous conduction mode across the full charge cycle, eliminating high inrush currents. Its output voltage sensing uses flyback pulse monitoring on the SW pin-no external resistor divider or zener diode required.
It features a user-programmable refresh timer (via CT pin capacitor), open-collector DONE output for charge-status signaling, and CHARGE pin logic-level enable/shutdown with low-to-high transition forcing recharge. The internal NPN power switch has 50V DC breakdown and 38V dynamic blocking capability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Peak Switch Current | 1.0A typical - sets maximum primary-side energy transfer per cycle |
| Input Current Limit | 450mA - ensures stable operation from two AA cells or 1.8V–16V supply |
| SW Pin Breakdown | 50V DC - enables use with higher-turns-ratio transformers vs. LT3420 (38V) |
| Secondary Current Limit | 15mA typical - defines minimum secondary conduction threshold for switch re-enable |
| Refresh Timer Thresholds | 0.5V (lower) / 1.0V (upper) - determines CT capacitor charge/discharge timing window |
| Operating Temp Range | –40°C to +85°C - qualified for consumer and industrial camera environments |
| Package | 10-Lead MSOP - 3mm × 3mm footprint with exposed pad (GND) for thermal management |
Pinout & Package
LT3420EMS-1#PBF is housed in a 10-lead plastic MSOP package with exposed pad (GND). Pin 11 (exposed pad) must be soldered to PCB ground plane for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RREF (1) | Reference resistor connection | Sets internal 1V reference bias; 2kΩ to GND recommended |
| VBAT (2) | Battery input supply | Primary power source for transformer primary; supports 1.8V–16V |
| RFB (3) | Feedback current input | Receives current proportional to VOUT/N; no external divider needed |
| VCC (4) | IC supply rail | Must be bypassed with ≥4.7µF ceramic capacitor; 2.5V–16V range |
| GND (5) | Signal and power ground | Common reference for all analog and digital circuitry |
| SW (6) | Internal NPN switch collector | Drives transformer primary; 50V DC-rated, 38V dynamic-blocking |
| SEC (7) | Transformer secondary return | Connects to secondary winding center-tap or low-side node |
| DONE (8) | Open-collector status output | Pulled low during charging; high when capacitor fully charged |
| CHARGE (9) | Enable/shutdown control | ≥1.5V = active charge; ≤0.2V = shutdown; rising edge forces recharge |
| CT (10) | Refresh timer capacitor | External capacitor sets refresh interval: CT = 2.5µF × tREFRESH |
Key Features
| Feature | Design Value |
|---|---|
| Flyback voltage sensing | Eliminates need for output voltage divider or zener diode, reducing BOM count and layout area |
| Automatic refresh mode | Maintains capacitor charge at ~2mA average input current, configurable via CT pin capacitor |
| Controlled input current limit | 450mA max ensures stable operation from low-voltage sources like two AA cells |
| Adaptive off-time control | Maintains continuous conduction mode across entire charge cycle, improving efficiency and reducing EMI |
| Charge-complete indicator | Open-collector DONE pin provides unambiguous system-level status for microcontroller polling or interrupt |
Applications
| Digital Camera Flash Unit | Film Camera Flash Unit |
|---|---|
Use Scenario: Rapid charging of 100µF photoflash capacitor to 320V in portable digital cameras with battery-powered operation. IC Role / Device Role / Timing Role: High-efficiency flyback controller managing transformer energy transfer, output voltage regulation, and charge-state signaling. Use Value: Achieves 3.5-second charge time from 5V while consuming only 450mA input current-enabling compact, long-life battery designs. | Use Scenario: Reliable high-voltage capacitor charging in mechanical film cameras with manual or auto-exposure systems. IC Role / Device Role / Timing Role: Standalone photoflash charger providing precise voltage hold and refresh without microcontroller intervention. Use Value: Maintains 320V output with <2mA average refresh current, extending shelf life of film camera flash modules. |
| High-Voltage Power Supplies | Portable Medical Imaging Flash |
Use Scenario: Generating stable 300–350V rails in compact, isolated auxiliary supplies for sensors or analog front-ends. IC Role / Device Role / Timing Role: Isolated DC-DC converter core with inherent output voltage sensing and programmable refresh. Use Value: Eliminates optocoupler feedback and external voltage references-reducing component count and board space by >30%. | Use Scenario: Charging flash capacitors in handheld ultrasound or dermatology devices requiring rapid, repeatable light pulses. IC Role / Device Role / Timing Role: Precision-controlled photoflash driver with deterministic charge timing and low quiescent current between pulses. Use Value: Enables sub-5-second recharge cycles and >10,000-shot operational lifetime on single-cell Li-ion batteries. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar photoflash capacitor charging applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3420EMS#PBF | 1.4A peak switch current, 840mA input limit, 38V SW pin rating, 220µF/320V charge in 3.7s | Better suited for larger-capacitance flash units requiring higher energy delivery | Select LT3420EMS#PBF when charging >150µF capacitors or operating with lower-turns-ratio transformers |
| MAX8632ETA+T | 36V max input, 1.2A switch current, integrated MOSFET, no refresh timer, requires external feedback divider | Lacks automatic refresh and flyback-sensing architecture-requires more external components | Choose MAX8632ETA+T only if board space permits additional resistors/diodes and refresh functionality is unnecessary |
Compared with LT3420EMS#PBF, the LT3420EMS-1#PBF trades peak current and charge speed for higher SW pin voltage rating and lower input current-making it optimal for compact, battery-constrained designs. The MAX8632ETA+T offers integration but lacks the LT3420EMS-1#PBF's self-sensing and refresh capabilities, increasing design complexity for maintenance-free operation.
Availability
LT3420EMS-1#PBF is available at Aetrix Electronics and suitable for digital camera flash units, film camera flash modules, high-voltage auxiliary power supplies, and portable medical imaging flash systems requiring stable component supply and long-term manufacturability.
Supply support for LT3420EMS-1#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 precision analog and power management portfolio with rigorous automotive and industrial qualification standards.
The LT3420 family was designed specifically for high-efficiency, low-component-count photoflash capacitor charging in space-constrained portable imaging systems-emphasizing adaptive control, integrated sensing, and autonomous refresh.
FAQ
What is the maximum output voltage the LT3420EMS-1#PBF can safely charge to?
The LT3420EMS-1#PBF is characterized to charge photoflash capacitors up to 320V, as verified in Figure 2 of the datasheet using a 100µF capacitor and Kijima SBL-5.6S-2 transformer. Its 50V SW pin DC rating and 38V dynamic blocking capability constrain safe operation to configurations where VOUT/N + VBAT ≤ 50V. For 320V output and 5V input, a minimum turns ratio of 10 is required-matching the documented 1:10 design.
Does the LT3420EMS-1#PBF require an external voltage divider or zener diode for output regulation?
No, the LT3420EMS-1#PBF does not require an external voltage divider or zener diode. Its output voltage sensing scheme monitors the flyback pulse on the SW pin to indirectly regulate output voltage-eliminating both components. This is confirmed in the "Photoflash Capacitor Chargers with Automatic Refresh" section and Figure 2 schematic, where no divider or zener appears in the feedback path.
How is the refresh interval programmed on the LT3420EMS-1#PBF?
The refresh interval on the LT3420EMS-1#PBF is set by an external capacitor on the CT pin, using the formula CT = 2.5 µF × tREFRESH, where tREFRESH is the desired period in seconds. A 100nF capacitor yields ~40ms refresh, while 1µF gives ~400ms. Grounding CT disables refresh entirely, requiring CHARGE pin toggling to restart charging-per the "Operation" section and Figure 5 waveform annotation.
What is the function of the DONE pin on the LT3420EMS-1#PBF?
The DONE pin on the LT3420EMS-1#PBF is an open-collector NPN output that signals charge completion: it is pulled low during active charging and goes high (when externally pulled up) when the photoflash capacitor reaches the target voltage and power delivery stops. This behavior is explicitly defined in the "Pin Functions" section and demonstrated in Figure 5's oscillograph, where DONE transitions high at the end of the charging phase.
Can the LT3420EMS-1#PBF be used with a 3.3V supply instead of 5V?
Yes, the LT3420EMS-1#PBF supports input supplies from 1.8V to 16V on both VBAT and VCC pins, including 3.3V operation. Figure G14 and G15 show input current vs. VOUT curves measured at VCC = VBAT = 3.3V, and the Electrical Characteristics table specifies VCC min = 2.5V (typ) and VBAT min = 1.8V-confirming robust 3.3V compatibility for low-power camera modules.
LT3420EMS-1#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-1#PBF FAQ
1.How can I place an order for LT3420EMS-1#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3420EMS-1#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-1#PBF reliable?
The price and inventory of LT3420EMS-1#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-1#PBF is usually 5 days.
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Once your LT3420EMS-1#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-1#PBF?
For technical support, including LT3420EMS-1#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3420EMS-1#PBF requirements.
6.How does Aetrix verify that LT3420EMS-1#PBF is sourced from the original manufacturer or authorized distributors?
All LT3420EMS-1#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-1#PBF meets industry standards.
7.What is the process for return or replacement of LT3420EMS-1#PBF?
All LT3420EMS-1#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3420EMS-1#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-1#PBF part is unused and in its original packaging.
Return procedure for LT3420EMS-1#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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