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Microchip Technology MIC3172BM
- Part No.:
- MIC3172BM
- Manufacturer:
- Microchip Technology
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MIC3172BM.pdf
- Description:
- IC REG BUCK BOOST 1.25A 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,210
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Product details
Overview
MIC3172BM from Microchip Technology is a 100 kHz current-mode PWM controller IC with integrated 65V/1.25A NPN power switch, designed for step-up, step-down, inverting, and flyback topologies. It features TTL-compatible enable/shutdown control (EN pin), 3V–40V input range, 7 mA operating quiescent current, and <1 µA shutdown current-enabling efficient battery-powered DC-DC conversion in compact portable systems.
For engineers reviewing the MIC3172BM datasheet, MIC3172BM pinout, MIC3172BM application, or MIC3172BM equivalent, key selection considerations include its dedicated EN pin for precise on/off control, dual power ground pins (PGND1/PGND2) enabling configurable current limiting, floating switch architecture supporting multiple topologies, and compatibility with LT1172 sockets in legacy designs.
Technical Context
The MIC3172BM implements fixed-frequency (88–112 kHz) current-mode control using an internal 1.24 V reference and transconductance error amplifier. Its PWM logic integrates cycle-by-cycle current limiting via internal 0.3 Ω sense resistors across PGND1 and PGND2, with anti-saturation circuitry improving duty cycle utilization.
Unlike the MIC2172, the MIC3172BM replaces SYNC functionality with a TTL-level EN input (VEN_TH = 0.4–2.4 V), allowing direct logic-driven enable/disable without external level-shifting. Shutdown reduces supply current to <1 µA while preserving pin-compatible footprint with the MIC2172 in 8-pin DIP packages.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Rating | 65 V breakdown voltage, 1.25 A continuous current limit-supports up to 50 W off-line converters with external switch or self-contained low-to-mid power regulation. |
| Input Voltage Range | 3.0 V to 40 V-enables operation from single Li-ion cells up to industrial 24 V rails without external regulators. |
| Oscillator Frequency | 88–112 kHz typical (100 kHz nominal)-provides predictable EMI profile and allows use of small magnetics in space-constrained designs. |
| Quiescent Current | 7 mA (operating), <1 µA (shutdown)-extends battery life in always-on or intermittently active portable equipment. |
| Enable Threshold | 0.4 V (low), 2.4 V (high)-guarantees robust TTL/CMOS logic interface without pull-up resistors or level translators. |
| Feedback Reference | 1.240 V ±24 mV-sets output voltage accuracy via external resistor divider; line regulation ≤0.07 %/V ensures stability across wide VIN range. |
| Thermal Range | –40°C to +85°C ambient-validated for industrial and automotive cabin-temperature environments. |
Pinout & Package
The MIC3172BM is housed in an 8-pin plastic DIP (Dual In-line Package) with through-hole mounting, rated for –40°C to +85°C ambient operation and featuring 130°C/W junction-to-ambient thermal resistance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (SGND) | Signal Ground | Analog reference ground for error amplifier and feedback network-must be isolated from power grounds to prevent noise coupling into regulation loop. |
| 2 (COMP) | Compensation Output | Transconductance amplifier output used for loop stabilization, soft-start timing, or current limit tailoring via external RC networks. |
| 3 (FB) | Feedback Input | Inverting input of error amplifier-connected to resistive divider to set regulated output voltage with 1.24 V reference. |
| 4 (EN) | Enable Control | TTL-compatible digital input: high (>2.0 V) enables switching; low (<0.4 V) disables regulator and reduces IQ to <1 µA. |
| 5 (VIN) | Supply Input | Main power input (3–40 V); powers internal 2.3 V bias regulator and all circuitry except when EN = low. |
| 6 (PGND2) | Power Ground #2 | Emitter connection of internal NPN switch with 0.3 Ω current sense-required connection point for inductor or input ground return path. |
| 7 (VSW) | Switch Collector | Collector of internal NPN power transistor-connects to inductor (boost/flyback) or input rail (buck) depending on topology. |
| 8 (PGND1) | Power Ground #1 | Second emitter with 0.3 Ω sense resistor-optional connection; floating reduces current limit by 50%, enabling safe derating. |
Key Features
| Feature | Design Value |
|---|---|
| Dedicated EN pin | Enables deterministic system-level power sequencing and sleep/wake control without modifying oscillator or feedback paths. |
| Floating switch architecture | Supports boost, buck, inverting, Cuk, and flyback topologies from a single IC-reducing BOM count and design validation effort. |
| Dual PGND pins with current scaling | PGND1 float option cuts maximum switch current to 0.625 A-allowing safe operation at reduced thermal load without component change. |
| Internal cycle-by-cycle current limit | Prevents switch destruction during overload or short-circuit events without external sensing components or protection ICs. |
| Low external parts count | Requires only inductor, diode, output capacitor, and two feedback resistors-minimizing PCB area and assembly cost in cost-sensitive applications. |
Applications
| Laptop Power Management | Handheld Instrument Supply |
|---|---|
Use Scenario: Regulating 5 V USB input to 12 V for LCD backlight or sensor bias in ultra-thin notebooks. IC Role / Device Role / Timing Role: Primary DC-DC controller providing stable 12 V output with fast transient response and low-noise operation. Use Value: Enables single-stage conversion without external MOSFET drivers, reducing solution size and component count versus discrete controllers. | Use Scenario: Generating ±5 V rails from a single 9 V alkaline battery in portable multimeters or data loggers. IC Role / Device Role / Timing Role: Dual-rail flyback controller implementing isolated negative output via transformer winding polarity reversal. Use Value: Eliminates need for separate charge-pump or inverter ICs-cutting bill-of-materials and simplifying layout in handheld enclosures. |
| Toy Motor Drive Supply | Off-Line AC/DC Adapter (≤50 W) |
Use Scenario: Providing regulated 6 V output from 3–4.2 V LiPo battery to drive precision servo motors in educational robotics kits. IC Role / Device Role / Timing Role: Step-up controller with programmable soft-start to prevent motor jerk during power-on. Use Value: Built-in EN pin allows MCU-controlled motor activation, while <1 µA shutdown current preserves battery shelf life for months. | Use Scenario: Secondary-side regulation in universal-input 24 V/2 A offline adapters for IoT gateways and smart home hubs. IC Role / Device Role / Timing Role: Flyback controller operating in discontinuous conduction mode (DCM) with fixed 100 kHz frequency for predictable EMI filtering. Use Value: Integrated 65 V switch eliminates need for external HV MOSFET and driver, reducing transformer turns ratio and core size. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MIC2172BM | Replaces EN with SYNC pin; supports external frequency synchronization up to 135 kHz and master/slave configuration. | Suitable for multi-regulator systems requiring synchronized switching to avoid beat frequencies-unsuitable where logic-level enable is mandatory. | Select MIC2172BM only if synchronization is required; otherwise MIC3172BM offers simpler control with identical topology support and package. |
| LT1172CN8#PBF | No dedicated enable pin; shutdown achieved by pulling VC (COMP) below 0.15 V-requires additional transistor or logic gate for TTL compatibility. | Legacy part with identical pinout but higher quiescent current (10 mA vs. 7 mA) and no guaranteed <1 µA shutdown mode. | Use LT1172CN8#PBF only for drop-in replacement in existing designs; MIC3172BM provides superior efficiency and native logic control. |
Compared with MIC2172BM and LT1172CN8#PBF, the MIC3172BM delivers lower standby power, simpler enable interfacing, and identical topology flexibility-making it optimal for new designs prioritizing battery life and system-level controllability over synchronization or legacy compatibility.
Availability
MIC3172BM is available at Aetrix Electronics and suitable for laptop power management, handheld instrument supply, toy motor drive, and off-line AC/DC adapter applications requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for MIC3172BM 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
Microchip Technology is a U.S.-based semiconductor manufacturer specializing in microcontrollers, analog devices, and power management ICs, with a focus on reliability, longevity, and industrial-grade qualification.
The MIC3172BM belongs to Microchip's legacy high-voltage PWM controller product line, engineered specifically for cost-sensitive, space-constrained DC-DC conversion in portable and consumer electronics where integration, efficiency, and ease of use are critical.
FAQ
What is the maximum output power achievable with the MIC3172BM in a flyback configuration?
The MIC3172BM supports up to 50 W in off-line flyback converters when used with an external power switch. With its internal 65 V/1.25 A switch, practical output power is limited to ~15 W in continuous conduction mode due to thermal constraints in the 8-pin DIP package. Derating PGND1 or optimizing heatsinking extends usable power range while maintaining reliability-MIC3172BM datasheet Section 5.6 provides full thermal calculation methodology.
Can the MIC3172BM replace the LT1172 in existing designs without board modifications?
Yes-the MIC3172BM uses the same 8-pin DIP footprint and pinout as the LT1172, but requires adaptation of the shutdown method: LT1172 uses VC (pin 2) for disable, whereas MIC3172BM uses EN (pin 4). For non-shutdown circuits, tie EN to VIN; for shutdown-enabled designs, connect EN to the existing logic signal driving the LT1172's shutdown transistor-MIC3172BM eliminates that transistor, simplifying the circuit.
How does floating PGND1 affect the MIC3172BM's current limit and thermal performance?
Leaving PGND1 unconnected reduces the MIC3172BM's effective current limit by 50% (to ~0.625 A), directly lowering conduction losses and junction temperature under load. This derating improves thermal margin without changing external components-ideal for applications where peak current demand is intermittent or well below 1.25 A, and where board-level heatsinking is impractical.
What is the minimum input voltage required for the MIC3172BM to start switching?
The MIC3172BM begins switching at a minimum input voltage of 2.7 V (typical) and guarantees operation down to 3.0 V across temperature. Below 2.7 V, internal 2.3 V bias regulator cannot sustain full functionality-startup behavior becomes unpredictable. For Li-ion battery applications, this allows reliable operation down to nearly depleted cell voltage (~3.0 V), extending usable runtime before system shutdown-MIC3172BM Electrical Characteristics Table confirms VIN(MIN) = 2.7 V typ.
Does the MIC3172BM support soft-start, and how is it implemented?
Yes-the MIC3172BM supports two soft-start methods via the COMP pin: (1) A diode-capacitor network from COMP to ground slows error amplifier ramp-up, delaying output voltage rise; (2) A capacitor from FB to output creates dv/dt-dependent feedback that limits initial duty cycle. Both methods prevent inrush current and overshoot-MIC3172BM Applications Information Section 5.4 details component selection and layout guidance for each approach.
MIC3172BM Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Discontinued at Digi-Key
- Function:
- Step-Up, Step-Down, Step-Up/Step-Down
- Output Configuration:
- Positive or Negative
- Topology:
- Buck, Boost, Cuk, Flyback, Forward Converter
- Output Type:
- -
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- 1.25A
- Frequency - Switching:
- 100kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MIC3172BM FAQ
1.How can I place an order for MIC3172BM through Aetrix?
Please submit a Request for Quotation (RFQ) for MIC3172BM 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 MIC3172BM reliable?
The price and inventory of MIC3172BM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MIC3172BM is usually 5 days.
3.What payment methods are accepted for MIC3172BM?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MIC3172BM transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MIC3172BM?
MIC3172BM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MIC3172BM 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 MIC3172BM?
For technical support, including MIC3172BM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MIC3172BM requirements.
6.How does Aetrix verify that MIC3172BM is sourced from the original manufacturer or authorized distributors?
All MIC3172BM 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 MIC3172BM meets industry standards.
7.What is the process for return or replacement of MIC3172BM?
All MIC3172BM units undergo pre-shipment inspection (PSI). If there is an issue with MIC3172BM, 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 MIC3172BM part is unused and in its original packaging.
Return procedure for MIC3172BM:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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