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Microchip Technology MIC3172BN
- Part No.:
- MIC3172BN
- Manufacturer:
- Microchip Technology
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
MIC3172BN.pdf
- Description:
- IC REG BUCK BOOST 1.25A 8PDIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,102
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Product details
Overview
MIC3172BN from Microchip Technology is a 100 kHz current-mode PWM controller IC with integrated 65 V / 1.25 A NPN power switch, designed for step-up, flyback, inverting, and Cuk topologies in battery-powered and off-line DC-DC converters. It features TTL-compatible enable/shutdown control (EN pin), 3–40 V input range, 7 mA operating quiescent current, and <1 µA shutdown current.
For engineers reviewing the MIC3172BN datasheet, MIC3172BN pinout, MIC3172BN application, or MIC3172BN equivalent, key selection criteria include its dedicated EN logic interface, internal cycle-by-cycle current limiting, floating switch architecture enabling multiple topologies, low external component count, and compatibility with LT1172 sockets in retrofit designs.
Technical Context
The MIC3172BN implements current-mode control using an internal transconductance error amplifier (3.9 µA/mV typical gain) and a 100 kHz oscillator with 89% typical maximum duty cycle. Its dual-emitter NPN switch (PGND1/PGND2) enables configurable current limiting-floating PGND1 halves the 1.25 A switch rating-and its anti-saturation diode extends usable duty cycle by reducing Q1 turn-off delay.
Operation relies on a precision 1.24 V bandgap reference and 2.3 V internal regulator. The EN pin directly controls internal biasing: high enables full functionality; low disables all circuitry except leakage paths, reducing supply current to <1 µA. Feedback is applied to the FB pin (1.24 V threshold), while COMP provides transconductance output for loop compensation, soft-start, and current limit tailoring.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switch Rating | 65 V breakdown voltage, 1.25 A continuous current limit at 50% duty cycle - defines max input/output voltage differential and peak load capability in boost/flyback designs. |
| Input Voltage Range | 3.0 V to 40 V - supports single-cell Li-ion up to 24 V industrial rails without external pre-regulation. |
| Oscillator Frequency | 88–112 kHz (typ. 100 kHz) - sets switching frequency for magnetics sizing and EMI filtering; fixed, not adjustable. |
| Quiescent Current | 7 mA (operating), <1 µA (shutdown) - enables long battery life in portable devices with on/off control via EN. |
| Feedback Reference | 1.240 V ±24 mV - precise voltage setpoint for output regulation; line regulation ≤0.07 %/V ensures stability across input range. |
| Enable Threshold | VEN_TH = 0.4–2.4 V - TTL-compatible logic interface; EN < 0.4 V forces shutdown, EN > 2.4 V guarantees full enable. |
| Thermal Range | –40°C to +85°C ambient - validated for industrial and consumer environments; junction limit +125°C. |
Pinout & Package
The MIC3172BN is housed in an 8-pin plastic DIP (Dual In-line Package) with through-hole mounting and 0.3 inch lead spacing, rated for –40°C to +85°C ambient operation.
| 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. |
| 2 (COMP) | Compensation Output | Transconductance amplifier output used for loop stabilization, soft-start timing, or current limit clamping - high-impedance node requiring RC network to ground or FB. |
| 3 (FB) | Feedback Input | Inverting input of error amplifier; connects to resistive divider to set regulated output voltage via 1.24 V reference. |
| 4 (EN) | Enable Control | TTL-level digital input: high (>2.4 V) enables switching; low (<0.4 V) disables all internal circuitry except leakage paths. |
| 5 (VIN) | Power Supply Input | Main DC input (3–40 V); powers internal regulator and bias circuits - minimum start-up voltage is 2.7 V. |
| 6 (PGND2) | Power Ground #2 | Emitter of internal NPN switch; required connection point for inductor or input ground depending on topology. |
| 7 (VSW) | Switch Collector | Collector of internal NPN switch; connects to inductor (boost), transformer primary (flyback), or output capacitor (inverting). |
| 8 (PGND1) | Power Ground #1 | Second emitter with 0.3 Ω sense resistor; optional connection - floating reduces current limit by 50% for lower-power designs. |
Key Features
| Feature | Design Value |
|---|---|
| Dedicated TTL Enable Input | EN pin accepts standard logic levels to fully disable internal biasing, achieving <1 µA shutdown current - eliminates need for external MOSFET high-side switches in battery systems. |
| Floating Switch Architecture | Independent collector (VSW) and dual-emitter (PGND1/PGND2) terminals allow implementation of boost, flyback, inverting, and Cuk topologies without external level-shifting components. |
| Cycle-by-Cycle Current Limit | Internal sensing limits peak switch current to 1.25 A (duty-cycle dependent), protecting against overload and short-circuit faults without external current-sense resistors. |
| Low External Component Count | Requires only inductor, diode, output capacitor, and two feedback resistors - no external oscillator, driver, or current-sense circuitry needed. |
| LT1172 Socket Compatibility | Pinout matches LT1172 DIP package; EN pin replaces LT1172's VC pin function - enables drop-in replacement in legacy designs with minimal board modification. |
Applications
| Laptop Power Management | Handheld Instrument DC-DC |
|---|---|
Use Scenario: Generating 12 V from a 5 V USB or Li-ion battery rail to power analog front-ends and display backlights in portable test equipment. IC Role / Device Role / Timing Role: Primary current-mode PWM controller with integrated switch; regulates output via FB pin while EN enables/disables during sleep/wake cycles. Use Value: 7 mA quiescent current extends battery runtime; <1 µA shutdown eliminates standby drain; compact DIP footprint simplifies layout in space-constrained enclosures. | Use Scenario: Providing isolated 5 V output from 4–6 V input in handheld multimeters or data loggers using flyback topology. IC Role / Device Role / Timing Role: Flyback controller with VSW driving transformer primary and PGND2 tied to input ground; EN synchronizes power-on with microcontroller wake signal. Use Value: Floating switch architecture enables safe isolation without optocoupler feedback complexity; 65 V switch rating accommodates reflected voltage spikes in flyback designs. |
| Off-Line 50 W Converter | Predriver for Higher-Power SMPS |
Use Scenario: Building a 50 W offline AC-DC converter (e.g., 120 VAC → 24 VDC) using external MOSFETs driven by MIC3172BN's VSW output. IC Role / Device Role / Timing Role: Master controller generating gate drive signals; VSW drives external high-voltage N-channel MOSFET via level shifter; EN manages system-level power sequencing. Use Value: Internal 100 kHz oscillator provides stable timing reference; current-mode control ensures fast transient response to load steps; 40 V VIN rating supports rectified AC inputs up to ~56 VDC. | Use Scenario: Driving external high-current IGBTs or MOSFETs in motor control or lighting inverters where higher power than 1.25 A is required. IC Role / Device Role / Timing Role: Predriver supplying precisely timed, current-limited gate pulses; COMP output adjusts duty cycle based on feedback; EN coordinates multi-stage power-up. Use Value: Cycle-by-cycle current limiting protects external switches during fault conditions; 1.24 V FB reference allows accurate output voltage scaling; dual-emitter configuration supports source-follower or common-emitter gate drive configurations. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1172CN8#PBF | No dedicated EN pin; shutdown achieved by pulling VC pin below 0.15 V - requires external transistor or logic-level translator. | Legacy design compatibility; lacks TTL-enable simplicity and <1 µA shutdown current. | Select when replacing existing LT1172-based boards without modifying control logic; avoid for new designs requiring low-quiescent-power sequencing. |
| MIC2172BN | Replaces EN with SYNC pin for external frequency synchronization; same 100 kHz base frequency but adjustable up to 135 kHz via resistor. | Required in multi-regulator systems to eliminate audible beat frequencies; unsuitable where on/off control is mandatory. | Select when synchronizing multiple regulators from a master clock; avoid if enable/shutdown functionality is essential for power management. |
Compared with LT1172CN8#PBF, MIC3172BN offers simpler TTL-level enable control and superior shutdown current, while MIC2172BN trades enable capability for synchronization - making MIC3172BN optimal for battery-sensitive, single-regulator applications demanding precise power gating.
Availability
MIC3172BN is available at Aetrix Electronics and suitable for laptop power management, handheld instrument DC-DC conversion, and off-line 50 W converter designs requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for MIC3172BN 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 global semiconductor company specializing in microcontrollers, analog devices, and power management ICs, with a focus on reliability, longevity, and embedded system integration.
The MIC3172BN belongs to Microchip's legacy high-voltage PWM controller product line, engineered for cost-effective, low-component-count DC-DC conversion in portable, industrial, and consumer power supplies.
FAQ
What is the absolute maximum input voltage rating for the MIC3172BN?
The MIC3172BN has an absolute maximum input voltage (VIN) rating of 40 V. Exceeding this voltage may cause permanent damage. Its recommended operating input range is 3.0 V to 40 V, with a minimum start-up voltage of 2.7 V. The internal 2.3 V regulator ensures stable biasing across this range, and the 65 V switch breakdown voltage provides margin for transient spikes in flyback or boost configurations. Always observe derating guidelines for sustained operation near maximum ratings.
How does the EN pin on the MIC3172BN function in practical circuit design?
The EN pin on the MIC3172BN is a TTL-compatible digital input that directly controls internal biasing: applying >2.4 V enables full operation, while <0.4 V forces complete shutdown with <1 µA supply current. For new designs, connect EN to a microcontroller GPIO or logic gate; for LT1172 retrofits, replace the VC pull-down network with a direct EN-to-ground path. Never leave EN floating - tie to VIN or use a pull-up resistor to ensure reliable startup. The MIC3172BN's EN behavior is explicitly defined in its electrical characteristics table and functional block diagram.
Can the MIC3172BN be used in flyback converter topologies, and what pins are critical for that implementation?
Yes, the MIC3172BN is explicitly qualified for flyback operation per its datasheet General Description and Typical Application Circuits. Critical pins include VSW (drives transformer primary), PGND2 (connects to input ground or auxiliary winding return), and FB (monitors reflected output voltage via optocoupler or resistive divider). The floating switch architecture - with independent VSW collector and dual-emitter PGND1/PGND2 - eliminates need for external level shifters. A 5 V to 5 V flyback example is shown in DS20006208A-page 2, confirming direct applicability of MIC3172BN in isolated designs.
What is the purpose of the PGND1 pin on the MIC3172BN, and how does leaving it unconnected affect performance?
The PGND1 pin on the MIC3172BN is the second emitter of the internal NPN power switch, featuring a 0.3 Ω current-sense resistor in series. When left unconnected (floating), it reduces the effective current limit by approximately 50%, lowering the guaranteed switch current from 1.25 A to ~0.63 A at 50% duty cycle. This is a deliberate design feature for lower-power applications, reducing thermal stress and component count. Connecting PGND1 to PGND2 restores full 1.25 A capability. The MIC3172BN datasheet confirms this behavior in Section 3.0 (Pin Descriptions) and Section 5.5 (Current Limit).
Does the MIC3172BN support external frequency adjustment or synchronization like the MIC2172BN?
No, the MIC3172BN does not support external frequency adjustment or synchronization. Unlike the MIC2172BN - which features a SYNC pin for locking to external clocks or trimming frequency up to 135 kHz - the MIC3172BN substitutes that pin with EN for enable/shutdown control. Its oscillator is fixed at 100 kHz (88–112 kHz over temperature and supply), with no provision for external modulation. This distinction is clearly documented in the Functional Block Diagrams (DS20006208A-page 3), Pin Function Table (page 11), and Features list (page 1), confirming MIC3172BN's role as an on/off-controllable, non-synchronizable controller.
MIC3172BN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- 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:
- Through Hole
- Supplier Device Package:
- 8-PDIP
MIC3172BN FAQ
1.How can I place an order for MIC3172BN through Aetrix?
Please submit a Request for Quotation (RFQ) for MIC3172BN 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 MIC3172BN reliable?
The price and inventory of MIC3172BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MIC3172BN is usually 5 days.
3.What payment methods are accepted for MIC3172BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MIC3172BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MIC3172BN?
MIC3172BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MIC3172BN 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 MIC3172BN?
For technical support, including MIC3172BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MIC3172BN requirements.
6.How does Aetrix verify that MIC3172BN is sourced from the original manufacturer or authorized distributors?
All MIC3172BN 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 MIC3172BN meets industry standards.
7.What is the process for return or replacement of MIC3172BN?
All MIC3172BN units undergo pre-shipment inspection (PSI). If there is an issue with MIC3172BN, 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 MIC3172BN part is unused and in its original packaging.
Return procedure for MIC3172BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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