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Analog Devices Inc. LT3420EDD#PBF
- Part No.:
- LT3420EDD#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Power Management - Specialized
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3420EDD#PBF.pdf
- Description:
- IC PHOTOFLASH CAP CHARGER 10-DFN
- Quantity:
- Payment:
- Shipping:
Inventory:101
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Product details
Overview
LT3420EDD#PBF from Analog Devices (formerly Linear Technology) is a high-efficiency flyback photoflash capacitor charger IC with integrated 1.4A NPN power switch, adaptive off-time control, and automatic refresh. It charges a 220µF capacitor to 320V from 5V in 3.7 seconds, supports input supply from 1.8V to 16V, and operates in 10-lead (3mm × 3mm) DFN package with exposed GND pad. Used in digital camera flash units requiring fast, controlled high-voltage charging.
For engineers reviewing the LT3420EDD#PBF datasheet, LT3420EDD#PBF pinout, LT3420EDD#PBF application, or LT3420EDD#PBF equivalent, key selection criteria include primary current limit (1.4A), SW pin breakdown voltage (38V), refresh timer programmability via CT pin, and absence of external output voltage divider or Zener diode.
Technical Context
The LT3420EDD#PBF employs adaptive off-time control to maintain current-limited continuous conduction mode across the full charge cycle, eliminating high inrush current. Its output voltage sensing uses flyback pulse monitoring on the SW pin - not direct feedback - enabling regulation without RFB divider or Zener diode.
It integrates a 1.4A NPN switch with 340mV typical VCE(SAT), 200ns leakage blanking, and a dedicated refresh timer with user-programmable period via external CT capacitor. The DONE pin provides open-collector charge-complete signaling, while CHARGE pin enables/disables operation and forces re-entry into charging mode.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | Up to 320V - supports standard photoflash capacitor charging without external scaling. |
| Primary Switch Current Limit | 1.4A (typ) - sets maximum energy per cycle; determines transformer sizing and charge rate. |
| SW Pin Breakdown Voltage | 38V - defines maximum reflected flyback voltage; constrains transformer turns ratio selection. |
| Input Supply Range | 1.8V to 16V - enables operation from two AA cells (≈3V) or wide-input industrial rails. |
| Charge Time (220µF → 320V) | 3.7s from 5V - quantifies system-level flash readiness; validated in Figure 1 reference design. |
| Refresh Timer Control | CT pin with 2.5µA charge/discharge current - allows precise, user-defined hold-time between refresh cycles. |
| Package | 10-Lead (3mm × 3mm) DFN with exposed GND pad - ensures thermal performance and compact layout for space-constrained cameras. |
Pinout & Package
LT3420EDD#PBF is housed in a 10-lead (3mm × 3mm) plastic DFN package with exposed GND pad (Pin 11), which must be soldered to PCB ground plane for thermal and electrical integrity.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RREF (1) | Reference resistor connection | Sets internal 1V reference bias; 2kΩ to GND establishes feedback scaling baseline. |
| VBAT (2) | Battery/primary supply input | Directly powers transformer primary; requires local 4.7µF ceramic bypass. |
| RFB (3) | Feedback current input | Receives current proportional to VOUT/N during flyback; enables dividerless regulation. |
| VCC (4) | IC bias supply | Provides internal circuitry power; must be ≥2.5V and bypassed with ≥4.7µF ceramic. |
| GND (5) | Ground reference | Common return for analog/digital circuits; connects to exposed pad (Pin 11). |
| SW (6) | Internal NPN switch collector | Drives transformer primary; high dv/dt node - minimize trace area to reduce EMI. |
| SEC (7) | Transformer secondary connection | Connects to secondary winding start; polarity critical for proper flyback operation. |
| DONE (8) | Open-collector charge-complete flag | Pulled low during active charging; high-Z when capacitor fully charged - requires external pull-up. |
| CHARGE (9) | Enable/shutdown and mode trigger | ≥1.5V = enable/charge; ≤0.2V = shutdown; rising edge forces immediate charge restart. |
| CT (10) | Refresh timer capacitor node | External capacitor sets refresh interval: CT = 2.5µF × tREFRESH (seconds). |
Key Features
| Feature | Design Value |
|---|---|
| Flyback topology with adaptive off-time control | Maintains continuous conduction mode across entire charge cycle - improves efficiency >75% and eliminates inrush spikes. |
| Dividerless output voltage sensing | Monitors flyback pulse on SW pin to regulate VOUT - removes need for precision RFB divider or high-voltage Zener. |
| Programmable automatic refresh | CT pin controls refresh interval; holds capacitor at target voltage with ~2mA average input current - extends standby time. |
| Integrated 1.4A NPN power switch | Eliminates external transistor and gate driver - reduces BOM count and layout complexity in compact camera modules. |
| Charge-complete indicator (DONE) | Open-collector output signals full charge state - enables microcontroller synchronization without polling or ADC. |
Applications
| Digital Camera Flash Unit | Film Camera Flash Unit |
|---|---|
Use Scenario: Charging a 220µF photoflash capacitor to 320V within <4 seconds after shutter half-press in a compact digital camera. IC Role / Device Role / Timing Role: High-efficiency flyback controller with integrated switch, regulating output via flyback pulse sensing and managing refresh timing. Use Value: Enables rapid flash readiness without external voltage dividers or Zener diodes, reducing component count and board area by >30% vs. discrete solutions. | Use Scenario: Powering legacy film camera flash modules requiring stable 300–330V output from 3V alkaline batteries. IC Role / Device Role / Timing Role: Photoflash capacitor charger with ultra-low quiescent current (≤130µA) and battery-friendly 1.8V minimum input. Use Value: Extends battery life by supporting automatic refresh at ~2mA average input current while maintaining full charge voltage tolerance ±5V. |
| High-Voltage Power Supplies | Portable Medical Imaging Strobe |
Use Scenario: Generating isolated 320V DC for portable X-ray detector bias supplies or electrostatic sensors. IC Role / Device Role / Timing Role: Flyback controller with 38V SW pin rating and programmable refresh - enables transformer-based isolation without optocoupler feedback. Use Value: Achieves >75% typical efficiency at 320V output using standard off-the-shelf transformers (e.g., TDK SRW10EPC-U01H003), simplifying safety certification. | Use Scenario: Driving short-duration, high-intensity strobes in handheld ultrasound or dermatology devices requiring precise flash timing. IC Role / Device Role / Timing Role: Charge controller with deterministic DONE signal and CHARGE pin edge-triggered restart - enables µs-level flash synchronization. Use Value: Provides repeatable 3.7s charge time (220µF→320V) and sub-millisecond DONE assertion delay - critical for image capture timing accuracy. |
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 | Same electrical specs, but in 10-lead MSOP package (3mm × 3mm footprint, 0.8mm height); no exposed thermal pad. | Preferred where manual assembly or reflow profile limits DFN use; slightly lower thermal performance (θJA = 100°C/W vs. 43°C/W). | Select LT3420EMS#PBF only if DFN assembly capability is unavailable; identical functionality and pinout except package mechanicals. |
| LT3420EDD-1#PBF | Lower primary current limit (1.0A vs. 1.4A), higher SW pin DC rating (50V vs. 38V), no leakage blanking, optimized for 100µF→320V in 3.5s. | Better suited for smaller capacitors and higher-turn-ratio transformers; not drop-in for 220µF designs due to reduced energy-per-cycle. | Choose LT3420EDD-1#PBF only when charging ≤100µF to 320V; verify transformer turns ratio and primary inductance meet revised LPRI ≥ 15µH requirement. |
Compared with LT3420EDD#PBF, LT3420EMS#PBF offers identical electrical behavior in a more assembly-friendly package but sacrifices thermal performance, while LT3420EDD-1#PBF trades peak charge rate for higher voltage margin and smaller capacitor support - neither is pin-compatible nor functionally interchangeable without circuit redesign.
Availability
LT3420EDD#PBF is available at Aetrix Electronics and suitable for digital camera flash units, film camera flash modules, and portable high-voltage power supplies requiring stable component supply, consistent parametric performance, and long-term lifecycle support.
Supply support for LT3420EDD#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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies. Formerly Linear Technology, ADI acquired the LT product line in 2017.
The LT3420 product line was designed specifically for efficient, compact photoflash capacitor charging in battery-powered imaging systems - emphasizing minimal external components, high-voltage capability, and deterministic timing.
FAQ
What is the maximum output voltage achievable with the LT3420EDD#PBF?
The LT3420EDD#PBF is characterized to charge photoflash capacitors up to 320V, as verified in the Figure 1 reference design (220µF → 320V). While the flyback topology permits higher voltages depending on transformer turns ratio and diode rating, 320V represents the validated, production-ready operating point with standard components like the TDK SRW10EPC-U01H003 transformer and Vishay GSD2004S dual diode. Exceeding this requires careful validation of SW pin stress and secondary insulation.
Does the LT3420EDD#PBF require an external voltage divider or Zener diode for output regulation?
No, the LT3420EDD#PBF does not require an external voltage divider or Zener diode. Its output voltage is regulated by monitoring the flyback pulse amplitude on the SW pin during switch-off periods - a method that infers VOUT from the reflected voltage across the primary winding. This eliminates both the resistor divider network and high-voltage Zener diode traditionally needed in capacitor charger ICs, reducing component count and improving reliability.
How is the refresh interval programmed on the LT3420EDD#PBF?
The refresh interval on the LT3420EDD#PBF is programmed using an external capacitor connected from the CT pin (Pin 10) to GND. The relationship is linear: CT (in farads) = 2.5 × 10−6 × tREFRESH (in seconds). For example, a 2.5nF capacitor yields a 1-second refresh period. Grounding the CT pin disables refresh entirely, forcing manual re-triggering via the CHARGE pin.
What is the purpose of the DONE pin on the LT3420EDD#PBF?
The DONE pin on the LT3420EDD#PBF is an open-collector NPN output that signals charge completion. It is pulled low during active charging and goes high-impedance (requiring an external pull-up resistor) when the photoflash capacitor reaches the target voltage. This provides a clean, logic-compatible flag for microcontrollers to synchronize flash firing, enter low-power modes, or initiate diagnostics - without ADC sampling or software timing loops.
Can the LT3420EDD#PBF be used with input supplies below 2.5V?
Yes, the LT3420EDD#PBF supports input supplies as low as 1.8V on the VBAT pin, enabling operation from two fresh AA cells (~3.0V) or partially discharged batteries. However, the VCC pin requires a minimum of 2.2V (typical 2.5V) for internal circuitry - so a local LDO or charge pump may be needed if VBAT < 2.5V and no separate bias rail exists. The datasheet confirms guaranteed operation down to 1.8V on VBAT with appropriate VCC conditioning.
LT3420EDD#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- 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-DFN (3x3)
LT3420EDD#PBF FAQ
1.How can I place an order for LT3420EDD#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3420EDD#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 LT3420EDD#PBF reliable?
The price and inventory of LT3420EDD#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3420EDD#PBF is usually 5 days.
3.What payment methods are accepted for LT3420EDD#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3420EDD#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3420EDD#PBF?
LT3420EDD#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3420EDD#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 LT3420EDD#PBF?
For technical support, including LT3420EDD#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3420EDD#PBF requirements.
6.How does Aetrix verify that LT3420EDD#PBF is sourced from the original manufacturer or authorized distributors?
All LT3420EDD#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 LT3420EDD#PBF meets industry standards.
7.What is the process for return or replacement of LT3420EDD#PBF?
All LT3420EDD#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3420EDD#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 LT3420EDD#PBF part is unused and in its original packaging.
Return procedure for LT3420EDD#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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