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STMicroelectronics ST778ACD
- Part No.:
- ST778ACD
- Manufacturer:
- STMicroelectronics
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
ST778ACD.pdf
- Description:
- IC REG BOOST PROG 300MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,170
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Product details
Overview
ST778ACD from STMicroelectronics is a low-voltage, synchronous step-up DC-DC converter optimized for 3.0 V or 3.3 V fixed-output applications. It integrates a 1 A NPN power switch and synchronous PNP rectifier, supports 1 V to 6 V input, delivers up to 300 mA output current at 3.3 V (VIN ≥ 2.4 V), fully disconnects load in shutdown, and operates with only three external components: one 22 µH inductor and two capacitors.
For engineers reviewing the ST778ACD datasheet, ST778ACD pinout, ST778ACD application, or ST778ACD equivalent, key selection criteria include its adjustable current limit (via ILIM pin), 20 µA shutdown supply current, internal 1.25 V reference, SEL pin configuration for 3.0/3.3 V output selection, and DIP-8/SO-8 package compatibility with legacy board layouts.
Technical Context
The ST778ACD uses a current-mode PWM controller with integrated synchronous rectification, enabling regulation even when VIN exceeds VOUT. Its internal 1 A NPN switch and complementary PNP rectifier eliminate the need for an external catch diode and reduce conduction losses.
Shutdown mode disables both switching and rectifier action, fully isolating OUT from IN via internal transistor cutoff - a distinguishing feature versus conventional boost converters that leak through parasitic paths. The SEL pin selects between 3.0 V (open) and 3.3 V (grounded) fixed outputs without external feedback resistors.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 1 V to 6 V - guarantees reliable start-up under load down to 1 V, critical for single-cell alkaline or NiMH battery systems. |
| Output Voltage | 3.0 V (SEL open) or 3.3 V (SEL grounded) - factory-trimmed, no external resistors required for fixed-output operation. |
| Max Output Current | 300 mA at 3.3 V with VIN ≥ 2.4 V - limited by thermal dissipation in SO-8 (344 mW @ 85°C) and DIP-8 (550 mW). |
| Efficiency | 82% typical at 100 mA load - achieved via synchronous rectification and low RDS(on)-equivalent rectifier drop (0.18 V @ 400 mA). |
| Supply Current | 270 µA no-load, 20 µA in shutdown - enables ultra-low quiescent power in battery-backed standby modes. |
| Current Limit | Adjustable up to 1 A via ILIM pin - allows use of low-cost, low-saturation inductors while preventing thermal runaway during overload. |
Pinout & Package
ST778ACD is available in both SO-8 (surface-mount) and DIP-8 (through-hole) packages. Both share identical pin functions and thermal characteristics (Rthj-amb = 160 °C/W for SO-8, 100 °C/W for DIP-8).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 ILIM | Current limit programming input | Connect to IN for 1 A peak switch current; resistor divider sets lower limits - enables inductor optimization and fault current tailoring. |
| 2 IN | Main power input | Accepts 1–6 V DC source; supplies bias for internal circuitry and drives ILIM/SHDN thresholds referenced to VIN. |
| 3 AGND | Analog ground reference | Separate from PGND to minimize noise coupling into error amplifier and reference - must be tied to PGND near device. |
| 4 PGND | Power ground return | Low-impedance path for switch and rectifier currents - requires direct soldering to ground plane to limit voltage spikes and EMI. |
| 5 LX | Switch node | Drives external inductor; connects collector of NPN switch and emitter of PNP rectifier - high dv/dt node requiring short PCB traces. |
| 6 OUT | Regulated output | Delivers 3.0/3.3 V; requires 100 µF low-ESR capacitor placed adjacent to pin to suppress ripple and support transient response. |
| 7 SHDN | Active-low enable/shutdown control | Threshold at VIN/2 ± 0.25 V - asserts full system isolation when pulled low, reducing supply current to 20 µA. |
| 8 SEL | Output voltage select | Grounded → 3.3 V output; open → 3.0 V output - eliminates external feedback network for fixed-output designs. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous rectification | Integrated PNP rectifier replaces external Schottky diode, reducing forward drop to 0.18 V and improving light-load efficiency. |
| Full output disconnection | Both switch and rectifier turn off in shutdown - eliminates leakage paths and ensures true zero-load current draw from source. |
| Adjustable current limit | ILIM pin supports resistor-based scaling from ~200 mA to 1 A - enables cost-effective inductor selection without compromising short-circuit robustness. |
| Low-noise layout support | Dedicated AGND and PGND pins with separate internal routing - minimizes ground bounce and improves regulation accuracy under dynamic load. |
Applications
| Wireless Sensor Node Power | Portable Medical Device Supply |
|---|---|
Use Scenario: Single-cell alkaline/NiMH-powered temperature/humidity sensor transmitting intermittently via BLE or sub-GHz RF. IC Role / Device Role / Timing Role: Primary 3.3 V rail generator; regulates from decaying 1.0–1.6 V battery voltage while maintaining stable MCU and radio interface voltage. Use Value: 1 V start-up and 20 µA shutdown current extend battery life beyond 5 years in sleep-dominated duty cycles. | Use Scenario: Handheld pulse oximeter with OLED display, analog front-end, and microcontroller operating from two AA cells. IC Role / Device Role / Timing Role: Fixed 3.3 V supply for digital logic and ADC reference; powers display driver during brief measurement bursts. Use Value: Synchronous rectification sustains >80% efficiency across 1.8–3.0 V input range, minimizing heat in compact enclosure. |
| Industrial Data Logger | Smart Meter Backup Supply |
Use Scenario: Battery-backed data logger recording environmental parameters every 10 seconds in remote outdoor enclosures. IC Role / Device Role / Timing Role: Main 3.0 V supply for microcontroller and SPI flash memory; activated only during write/read cycles. Use Value: SEL pin configured for 3.0 V output matches low-power MCU VDD requirements without trimming resistors or calibration. | Use Scenario: Real-time clock and SRAM backup in electricity meters during main AC failure. IC Role / Device Role / Timing Role: Standby power converter energized from supercapacitor or coin cell; delivers regulated 3.3 V during brownout. Use Value: Full output disconnection prevents capacitor self-discharge through IC leakage, extending hold-up time by >30%. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-up converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS61022DRVR | Higher 2 MHz switching frequency; 0.9 V minimum input; integrated soft-start; no SEL pin - requires external feedback for 3.3 V. | Supports smaller inductors/caps but lacks true output isolation in shutdown (leakage ~1 µA). | Preferred for space-constrained designs needing higher efficiency above 100 mA; not drop-in due to different pinout and feedback architecture. |
| MAX756CSA+ | Fixed 3.3 V or 5 V output; 0.7 V min input; no synchronous rectifier; 120 µA no-load current; DIP-8/SO-8 compatible. | Lacks load disconnection in shutdown (output floats); lower efficiency (~75%) due to external diode loss. | Valid legacy replacement where synchronous rectification and zero-leakage shutdown are non-critical. |
Compared with TPS61022DRVR and MAX756CSA+, ST778ACD uniquely combines true output isolation in shutdown, 1 V start-up, and SEL-selectable fixed outputs - making it optimal for ultra-low-power, battery-life-critical applications where board space permits DIP-8/SO-8 footprints.
Availability
ST778ACD is available at Aetrix Electronics and suitable for wireless sensor nodes, portable medical devices, industrial data loggers, and smart meter backup supplies requiring stable component supply across long-lifecycle embedded programs.
Supply support for ST778ACD 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, mixed-signal, power, and microcontroller products for industrial, automotive, and consumer markets.
The ST777/778/779 family was engineered specifically for ultra-low-voltage, battery-powered systems requiring high-efficiency boost conversion with minimal external components and guaranteed start-up below 1.2 V.
FAQ
What is the function of the SEL pin on ST778ACD?
The SEL pin selects the fixed output voltage: grounded → 3.3 V output; left open → 3.0 V output. It directly configures internal resistor divider ratios and requires no external components. This differs from the ST779's FB pin, which supports adjustable outputs via external resistors.
Can ST778ACD operate with input voltage lower than 1.2 V?
No - the absolute minimum input voltage is 1 V per Absolute Maximum Ratings, but guaranteed start-up under load occurs only at ≥1 V (tested per datasheet Note 3). Operation below 1 V is not characterized and may fail to initiate switching or regulate properly.
Why does ST778ACD specify separate AGND and PGND pins?
AGND provides a quiet reference for the error amplifier and 1.25 V bandgap, while PGND carries high di/dt switch and rectifier return currents. Separating them prevents ground bounce from modulating regulation accuracy - especially critical at light loads and during transients.
Is ST778ACD still in active production?
ST778ACD is marked "Obsolete Product(s)" in the official datasheet revision (October 2002). However, Aetrix Electronics maintains legacy inventory and offers traceable, tested units for design continuity and repair programs where functional equivalence and footprint compatibility are required.
ST778ACD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Up
- Output Configuration:
- Positive
- Topology:
- Boost
- Output Type:
- Programmable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 1V
- Voltage - Input (Max):
- 6V
- Voltage - Output (Min/Fixed):
- 3V, 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 300mA (Switch)
- Frequency - Switching:
- -
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- 0°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
ST778ACD FAQ
1.How can I place an order for ST778ACD through Aetrix?
Please submit a Request for Quotation (RFQ) for ST778ACD 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 ST778ACD reliable?
The price and inventory of ST778ACD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ST778ACD is usually 5 days.
3.What payment methods are accepted for ST778ACD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ST778ACD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ST778ACD?
ST778ACD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ST778ACD 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 ST778ACD?
For technical support, including ST778ACD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ST778ACD requirements.
6.How does Aetrix verify that ST778ACD is sourced from the original manufacturer or authorized distributors?
All ST778ACD 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 ST778ACD meets industry standards.
7.What is the process for return or replacement of ST778ACD?
All ST778ACD units undergo pre-shipment inspection (PSI). If there is an issue with ST778ACD, 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 ST778ACD part is unused and in its original packaging.
Return procedure for ST778ACD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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