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STMicroelectronics ST735SCD
- Part No.:
- ST735SCD
- Manufacturer:
- STMicroelectronics
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
ST735SCD.pdf
- Description:
- IC REG BUCK BST -5V 200MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,959
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Product details
Overview
ST735SCD from STMicroelectronics is a Bi-CMOS inverting switch-mode DC-DC regulator with integrated Power MOSFET, generating a fixed -5V output from +4.0V to +6.2V input. It delivers 200mA guaranteed output current, features 300kHz fixed-frequency current-mode PWM control, 0.8mA quiescent current, and ±5% output voltage accuracy over temperature and load. Used in HDD power rails and portable equipment requiring compact negative bias generation.
For engineers reviewing the ST735SCD datasheet, ST735SCD pinout, ST735SCD application, or ST735SCD equivalent, key selection criteria include its inverting topology, SO-8 package, -5V fixed output, shutdown current of 1µA, and compatibility with ceramic input/output capacitors and low-ESR inductors in space-constrained designs.
Technical Context
The ST735SCD employs current-mode PWM control with a factory-trimmed 300kHz oscillator for stable switching and low noise. Its internal Power MOSFET and integrated reference (1.225V) enable precise feedback regulation via external resistor dividers only in adjustable versions - the S-version fixes output at -5V without external feedback components.
It includes undervoltage lockout (3.5–4V threshold), soft-start (via SS pin), compensation network (CC pin, 7.5kΩ impedance), and thermal protection. The LX switch node supports peak currents up to 1.5A with 0.5Ω RDS(on), enabling efficient operation across -40°C to +125°C junction temperature range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed -5V ±5% over full temperature and load range - ensures stable bias for analog circuitry without external feedback tuning. |
| Input Voltage Range | +4.0V to +6.2V - compatible with single-cell Li-ion or regulated 5V rail inputs in portable systems. |
| Output Current | 200mA guaranteed above 4.5V input - sufficient for powering op-amp rails, sensor interfaces, or small logic families requiring negative supply. |
| Efficiency | 72% typical at 100mA load - minimizes thermal rise in sealed enclosures and extends battery life in portable applications. |
| Quiescent Current | 0.8mA typical - enables low-power standby modes while maintaining regulation readiness. |
| Shutdown Current | 1µA - allows deep sleep states in battery-powered devices without significant leakage drain. |
| Oscillator Frequency | 300kHz fixed - simplifies EMI filtering with standard ferrite beads and reduces size of passive components. |
Pinout & Package
ST735SCD is housed in an SO-8 surface-mount package (5.0mm × 6.2mm body, 1.27mm pitch), optimized for automated assembly and thermal performance with 8°C/W junction-to-case resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 SHDN | Shutdown Control Input | Active-high logic input; drives device into 1µA standby when pulled below 0.25V, resumes operation above 2V. |
| 2 VREF | Internal Reference Output | 1.225V ±50ppm/°C precision reference used internally for regulation - not user-accessible in ST735S variant. |
| 3 SS | Soft-Start Timing Node | Connects external capacitor to control startup slew rate and limit inrush current during power-up. |
| 4 CC | Compensation Network Input | Accepts RC network (7.5kΩ impedance) to stabilize loop response and prevent oscillation under varying loads. |
| 5 VOUT | Negative Output Terminal | Delivers regulated -5V output; requires low-ESR ceramic capacitor (≥10µF) placed adjacent to pin for stability. |
| 6 GND | Power and Signal Ground | Common return path for input, output, and internal circuitry - must be low-impedance plane to minimize noise coupling. |
| 7 LX | Switch Node Output | Drives external inductor; switches between VIN and GND at 300kHz; peak current capability 1.5A with 0.5Ω RDS(on). |
| 8 VIN | Positive Input Supply | Accepts +4.0V to +6.2V DC input; requires local 4.7µF X7R ceramic bypass capacitor within 5mm of pin. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting Topology with Integrated MOSFET | Eliminates need for external high-side switch and simplifies PCB layout for negative rail generation in tight spaces. |
| Current-Mode PWM Control | Provides inherent cycle-by-cycle current limiting and fast transient response to load steps without external compensation. |
| 300kHz Fixed Switching Frequency | Enables predictable EMI spectrum and consistent filter design using off-the-shelf 3–10MHz ferrite beads and MLCCs. |
| Undervoltage Lockout (UVLO) | Prevents erratic startup by disabling operation until input exceeds 3.5V, ensuring reliable turn-on behavior across battery discharge curves. |
| Low-Noise Operation with Soft Start | Reduces output voltage overshoot and input current spikes during startup, critical for noise-sensitive analog subsystems. |
Applications
| HDD Preamp Bias Supply | Portable Audio DAC Reference |
|---|---|
Use Scenario: Generating stable -5V bias for head preamplifier circuits in 2.5-inch hard disk drives. IC Role / Device Role / Timing Role: Inverting DC-DC regulator providing isolated negative rail from main 5V system bus. Use Value: Enables high-gain, low-noise amplification without cross-talk from shared ground paths or ripple-induced distortion. | Use Scenario: Supplying clean -5V reference to dual-supply audio DACs in battery-powered MP3 players. IC Role / Device Role / Timing Role: Negative voltage generator supporting rail-to-rail analog signal swing and minimizing THD+N. Use Value: Delivers 72% efficiency and 0.8mA quiescent current to extend playback time while maintaining SNR >95dB. |
| Industrial Sensor Interface | Medical Pulse Oximeter Front-End |
Use Scenario: Powering precision instrumentation amplifiers in 4–20mA loop-powered sensors. IC Role / Device Role / Timing Role: Compact negative rail source enabling bipolar signal conditioning from unipolar supply. Use Value: Achieves ±5% output accuracy over -40°C to +125°C, ensuring calibrated offset stability across environmental extremes. | Use Scenario: Providing isolated -5V for photodiode transimpedance amplifier stages in wearable pulse oximeters. IC Role / Device Role / Timing Role: Low-noise inverting regulator supporting sub-µV-level signal integrity in analog front-end chains. Use Value: 300kHz switching frequency avoids interference with IR/Red LED drive frequencies (typically 100–500Hz), preserving measurement fidelity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar inverting DC-DC regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX735CSA+ | Same -5V fixed output, 200mA rating, but uses external diode and requires larger inductor; 100kHz switching frequency. | Larger solution size and higher EMI susceptibility due to lower frequency and discrete rectification. | Select when legacy MAXIM footprint compatibility or availability outweighs size/efficiency trade-offs. |
| TPS60403DBVR | CMOS charge-pump inverter; no inductor required, but limited to 60mA output and 92% efficiency at light loads. | Not suitable for >100mA loads; lacks UVLO and soft-start, increasing risk of inrush damage in battery systems. | Choose only for ultra-low-noise, low-current (<60mA), inductor-free designs where efficiency at full load is secondary. |
Compared with MAX735CSA+ and TPS60403DBVR, ST735SCD offers superior power density (integrated MOSFET, SO-8), higher output current (200mA), and robust protection features (UVLO, soft-start), making it optimal for space-constrained, medium-power inverting applications demanding reliability and thermal efficiency.
Availability
ST735SCD is available at Aetrix Electronics and suitable for HDD preamp bias supplies, portable audio DAC references, and industrial sensor interfaces requiring stable component supply and long-term obsolescence management.
Supply support for ST735SCD 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, designing and manufacturing microcontrollers, power management ICs, and analog/mixed-signal devices for automotive, industrial, and consumer markets.
The ST735 series belongs to ST's legacy power conversion portfolio, specifically engineered for compact, high-efficiency inverting DC-DC regulation in portable and storage applications where board space and thermal constraints are critical.
FAQ
What is the maximum allowable input-to-output differential voltage for ST735SCD?
The absolute maximum input-to-output differential voltage is limited to VIN + |VOUT| < 12.7V per datasheet Absolute Maximum Ratings. With VOUT = -5V, this restricts VIN to ≤7.7V. Exceeding this risks permanent damage to the internal MOSFET and control circuitry, even if individual pin ratings appear compliant.
Can ST735SCD be used with tantalum output capacitors instead of ceramic?
No - the datasheet specifies X7R ceramic capacitors exclusively for CIN and COUT. Tantalum capacitors exhibit higher ESR and poorer high-frequency response, which destabilizes the current-mode control loop and may cause oscillation or excessive output ripple. Ceramic capacitance ≥10µF with low ESR is mandatory for stable operation.
Does ST735SCD require an external feedback resistor network to set output voltage?
No - the ST735SCD is the S-version, configured for fixed -5V output. Unlike the T-version (ST735TCD), it does not use the VFB pin for external feedback; the internal reference and regulation circuitry are hardwired to deliver -5V without external resistors. Adding feedback components will not alter output voltage and may impair regulation.
What is the recommended inductor value and saturation current rating for ST735SCD?
The datasheet recommends a 4.7µH inductor with saturation current >1.5A (peak LX current). A 6.8µH inductor improves current capability at same conditions. Core material must support 300kHz operation (e.g., shielded drum-core or molded ferrite); saturation current must exceed 1.5A to avoid inductance collapse and thermal runaway under full-load transients.
ST735SCD 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/Step-Down
- Output Configuration:
- Negative
- Topology:
- Buck-Boost
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4V
- Voltage - Input (Max):
- 6.2V
- Voltage - Output (Min/Fixed):
- -5V
- Voltage - Output (Max):
- -
- Current - Output:
- 200mA
- Frequency - Switching:
- 160kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
ST735SCD FAQ
1.How can I place an order for ST735SCD through Aetrix?
Please submit a Request for Quotation (RFQ) for ST735SCD 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 ST735SCD reliable?
The price and inventory of ST735SCD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ST735SCD is usually 5 days.
3.What payment methods are accepted for ST735SCD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ST735SCD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ST735SCD?
ST735SCD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ST735SCD 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 ST735SCD?
For technical support, including ST735SCD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ST735SCD requirements.
6.How does Aetrix verify that ST735SCD is sourced from the original manufacturer or authorized distributors?
All ST735SCD 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 ST735SCD meets industry standards.
7.What is the process for return or replacement of ST735SCD?
All ST735SCD units undergo pre-shipment inspection (PSI). If there is an issue with ST735SCD, 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 ST735SCD part is unused and in its original packaging.
Return procedure for ST735SCD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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