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Texas Instruments UC3870DW-2
- Part No.:
- UC3870DW-2
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
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UC3870DW-2.pdf
- Description:
- SWITCHING CONTROLLER
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Product details
Overview
UC3870DW-2 from Texas Instruments is a synchronous step-down (Buck) controller IC designed for high-efficiency DC/DC conversion in battery-powered systems. It supports 4.5–36 V input, delivers regulated output voltages from 2 V to 3.5 V (when paired with UC3910), operates up to 300 kHz, and features fixed-frequency average current mode control with integrated 10 V regulated gate drivers for external N-channel MOSFETs - enabling >90% efficiency in laptop CPU power supplies.
For engineers reviewing the UC3870DW-2 datasheet, UC3870DW-2 pinout, UC3870DW-2 application, or UC3870DW-2 equivalent, key selection criteria include UVLO thresholds (10 V turn-on / 9 V turn-off), bootstrap-regulated high-side drive (10.2 V typical), sleep-mode supply current (<75 µA), 2.5 V precision reference (±1% over temp), and compatibility with discrete synchronous rectification for low-RDS(on) loss optimization.
Technical Context
The UC3870DW-2 implements fixed-frequency average current mode control with inherent slope compensation via a 2.7 V peak-to-peak oscillator ramp, enabling stable regulation and superior line/load transient response. Its dual complementary 1 A gate drivers (HDRIVE/LDRIVE) feature non-overlapping timing (~200 ns dead time) and internal shoot-through prevention logic.
It integrates a 2.5 V ±1% reference (20 mA sink/source), X10 instrumentation amplifier for current sensing (common-mode range GND to VCC), and virtual 100% duty cycle operation via active bootstrap refresh when BOOT voltage falls below 8 V - critical for low-input LDO-like operation in battery discharge scenarios.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5 V to 36 V - supports wide battery input including 12 V nominal and 3-cell Li-ion stacks. |
| UVLO Turn-on/Off | 10.0 V / 9.0 V - ensures reliable startup only after sufficient rail stability for standard-power MOSFET gate drive. |
| Switching Frequency | Up to 300 kHz - enables compact magnetics and predictable EMI filtering without requiring external synchronization. |
| Reference Voltage | 2.500 V ±15 mV - provides precise feedback setpoint for ±1% output accuracy when used with UC3910 DAC interface. |
| Sleep Current | <75 µA - minimizes quiescent drain during system standby, extending battery life in portable devices. |
| Bootstrap Regulator | 10.2 V typical (UC3870-2) - sustains ≥10 V gate-source drive for high-side N-MOSFET even at high duty cycles. |
| Current Sense Gain | X10 instrumentation amplifier - converts 100 mV sense resistor drop into 1 V signal, reducing power loss and noise sensitivity. |
Pinout & Package
UC3870DW-2 is housed in an 18-pin SOIC (DW) package with 1.27 mm pitch, thermally optimized for surface-mount assembly in space-constrained power modules.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VCC | Positive supply rail | Primary IC power input (4.5–36 V); powers internal regulators and logic; UVLO threshold = 10 V. |
| BOOT | High-side gate drive rail | Provides bootstrapped voltage for HDRIVE; charges via external diode/Cbst; monitored for virtual 100% duty cycle support. |
| HDRIVE | High-side MOSFET gate driver | Complementary totem-pole output sourcing 500 mA/sinking 1 A; swings ~10 V above VCC when active. |
| LDRIVE | Low-side MOSFET gate driver | Complementary totem-pole output referenced to CAP; regulates VGS to ~10 V for optimal RDS(on) conduction. |
| ISNS+, ISNS− | Current sense differential inputs | Accept shunt voltage across external Rsense; feed X10 amp for accurate average current mode control. |
| VSNS | Voltage feedback inverting input | Connects to output voltage divider; sets regulation point relative to CMD reference (2–3.5 V range). |
| CMD | Voltage error amplifier non-inverting input | Accepts precision reference (e.g., UC3910 DAC output) to program output voltage in 100 mV steps from 2 V to 3.5 V. |
| SS | Soft-start and sleep control | Capacitor-based soft-start ramp; pulled low (<0.5 V) to enter ultra-low-power sleep mode (<75 µA ICC). |
| VREF | Precision 2.5 V reference output | Stable 2.5 V ±1% source/sink (20 mA max); disabled during UVLO or sleep for system-level power gating. |
| CT | Oscillator timing capacitor | Single external capacitor sets frequency (F ≈ 14250/CT); supports up to 300 kHz with 220 pF minimum. |
| COMP | Voltage amplifier output | Drives current amplifier; clamped at ~3.2 V to limit loop gain and prevent saturation. |
| CAO | Current amplifier output | Feeds PWM comparator; 0.1–4.0 V swing defines duty cycle command based on sensed vs. commanded current. |
| PGND | Power ground | High-current return path for MOSFET drivers; requires star grounding with low-side MOSFET source and output capacitor. |
| GND | Analog ground | Reference for all analog circuitry (amplifiers, references, CT); separate from PGND to avoid noise coupling. |
| CAP | Internal regulator bypass | Bypasses internal 11 V regulator (UC3870-2); supplies charge to BOOT via external diode; shorted to VCC for low-VIN operation. |
| CA− | Current amplifier inverting input | Receives filtered current feedback signal; connects to CAO via RC network for loop compensation. |
| ISOUT | X10 amplifier output | Level-shifted +2 V offset output (e.g., 3 V for 100 mV sense input); drives CA− to close current loop. |
| NC | No connect | Pins 1, 12, 13, 14, 15, 16, 17, 18 - unused; must remain unconnected per datasheet. |
Key Features
| Feature | Design Value |
|---|---|
| Fixed-frequency average current mode control | Eliminates need for external slope compensation while delivering tight load regulation and fast transient recovery. |
| Regulated 10 V gate drive outputs | Ensures consistent RDS(on) for both high- and low-side N-MOSFETs across input voltage and temperature. |
| Virtual 100% duty cycle operation | Active BOOT voltage monitoring and refresh enables LDO-like behavior down to ~4.5 V input without external circuitry. |
| Ultra-low sleep current (<75 µA) | Extends battery runtime in suspend states without requiring external enable/disable sequencing. |
| Integrated 2.5 V ±1% reference | Reduces BOM count by eliminating external reference IC; powers UC3910 or other peripheral circuitry directly. |
Applications
| Intel Pentium Pro CPU Power Supply | Laptop Core Voltage Regulation |
|---|---|
Use Scenario: Powers Intel Pentium Pro microprocessor requiring tightly regulated 2.5 V or 3.3 V at up to 20 A with fast load transients. IC Role / Device Role / Timing Role: Primary synchronous buck controller managing high-side/low-side MOSFET switching, current sensing, and voltage feedback loop. Use Value: Enables ±1% output accuracy and <10 µs transient response using UC3910 DAC interface and average current mode control. | Use Scenario: Regulates core voltage for mobile CPUs in battery-operated laptops with input ranging from 11 V (full battery) to 7 V (discharged). IC Role / Device Role / Timing Role: Synchronous step-down controller supporting LDO-like operation via bootstrap refresh and low-VIN gate drive optimization. Use Value: Delivers >92% efficiency at light loads and maintains regulation down to 4.5 V input without external assist circuitry. |
| Communications Baseband Power | Aerospace Avionics DC/DC Module |
Use Scenario: Supplies stable 2.8 V to RF baseband processors in cellular infrastructure equipment with strict ripple and noise requirements. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller synchronized to system clock via CT node coupling to minimize EMI interference. Use Value: Achieves <10 mVpp output ripple and <50 ns load-step recovery using programmable soft-start and high-bandwidth current loop. | Use Scenario: Provides MIL-STD-704 compliant 3.3 V power in avionics subsystems operating from 28 V aircraft bus with wide temperature range. IC Role / Device Role / Timing Role: High-reliability synchronous buck controller with extended temperature rating (0°C to +70°C), UVLO hysteresis, and robust gate drive protection. Use Value: Ensures fault-free startup and shutdown across –40°C to +85°C ambient via validated thermal performance and latch-free design. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC3870N-2 | DIP-18 package (through-hole); identical electrical specs and pinout; higher thermal resistance than SOIC. | Suitable for prototyping or legacy through-hole designs; not recommended for high-density PCBs. | Select UC3870N-2 only when manual assembly or socket-based testing is required. |
| UC2870DW-2 | Same SOIC-18 footprint but rated for –25°C to +85°C industrial temperature range (vs. 0°C to +70°C for UC3870DW-2). | Preferred for extended ambient environments where full commercial grade is insufficient but military grade is unnecessary. | Choose UC2870DW-2 if operating temperature exceeds +70°C but does not reach +85°C. |
Compared with UC3870DW-2, UC3870N-2 offers identical functionality in a through-hole package for ease of evaluation, while UC2870DW-2 extends operational temperature range - making the latter suitable for industrial edge nodes where ambient heat buildup occurs, and the former ideal for lab validation before SOIC migration.
Availability
UC3870DW-2 is available at Aetrix Electronics and suitable for laptop CPU power supplies, communications baseband regulation, and aerospace avionics DC/DC conversion requiring stable component supply, long-lifecycle support, and traceable sourcing.
Supply support for UC3870DW-2 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
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies with over 50 years of innovation in high-reliability power control ICs.
The UC3870 family belongs to TI's legacy high-performance synchronous buck controller product line, engineered specifically for battery-powered computing and communications systems demanding high efficiency, precision regulation, and robust gate drive capability.
FAQ
What is the UVLO threshold for UC3870DW-2?
The UC3870DW-2 has a VCC undervoltage lockout turn-on threshold of 10.0 V and turn-off threshold of 9.0 V, optimized for standard-power N-channel MOSFETs. This ensures gate drive remains stable and prevents erratic switching during brown-out conditions. The 1.0 V hysteresis avoids oscillation near the threshold, and these values are confirmed in the Absolute Maximum Ratings and Electrical Characteristics tables of the SLUS288A datasheet.
How does UC3870DW-2 achieve virtual 100% duty cycle operation?
The UC3870DW-2 monitors BOOT voltage continuously; if it falls below 8 V during high-duty-cycle operation, the IC automatically pulses LDRIVE to recharge the bootstrap capacitor (Cbst). This active refresh mechanism allows sustained conduction of the high-side MOSFET even at near-100% duty, enabling LDO-like regulation down to ~4.5 V input - a key feature verified in the Applications Information section of SLUS288A.
Can UC3870DW-2 be synchronized to an external clock?
Yes, UC3870DW-2 supports external synchronization: an AC-coupled clock signal can be injected at the CT pin via a small capacitor tied to ground through a low-value resistor. This technique is documented in TI Application Note U-111 and preserves fixed-frequency average current mode control while aligning switching edges to system timing - essential for EMI reduction in multi-rail power systems.
What is the purpose of the CMD pin on UC3870DW-2?
The CMD pin is the non-inverting input of the voltage error amplifier in UC3870DW-2 and accepts a precision reference voltage (e.g., from UC3910) to set the output voltage. With a 2 V to 3.5 V common-mode range and ±1% accuracy, it enables programmable 100 mV-step outputs - directly supporting Intel Pentium Pro and similar microprocessors. This function is explicitly defined in the Pin Descriptions and Applications Information sections of SLUS288A.
Does UC3870DW-2 integrate a precision voltage reference?
Yes, UC3870DW-2 includes an internal 2.5 V ±1% precision reference (VREF) capable of sourcing or sinking up to 20 mA. It is disabled during UVLO or sleep mode and features built-in short-circuit current limiting. This reference is used for internal error amplification and can power external circuitry such as DACs or monitoring ICs - specifications confirmed in the Electrical Characteristics table under "Reference Section" of SLUS288A.
UC3870DW-2 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Function:
- -
- Output Configuration:
- -
- Topology:
- -
- Output Type:
- -
- Number of Outputs:
- -
- Voltage - Input (Min):
- -
- Voltage - Input (Max):
- -
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- -
- Frequency - Switching:
- -
- Synchronous Rectifier:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
UC3870DW-2 FAQ
1.How can I place an order for UC3870DW-2 through Aetrix?
Please submit a Request for Quotation (RFQ) for UC3870DW-2 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 UC3870DW-2 reliable?
The price and inventory of UC3870DW-2 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3870DW-2 is usually 5 days.
3.What payment methods are accepted for UC3870DW-2?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3870DW-2 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3870DW-2?
UC3870DW-2 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC3870DW-2 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 UC3870DW-2?
For technical support, including UC3870DW-2 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3870DW-2 requirements.
6.How does Aetrix verify that UC3870DW-2 is sourced from the original manufacturer or authorized distributors?
All UC3870DW-2 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 UC3870DW-2 meets industry standards.
7.What is the process for return or replacement of UC3870DW-2?
All UC3870DW-2 units undergo pre-shipment inspection (PSI). If there is an issue with UC3870DW-2, 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 UC3870DW-2 part is unused and in its original packaging.
Return procedure for UC3870DW-2:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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