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NXP Semiconductors MC34129DR2
- Part No.:
- MC34129DR2
- Manufacturer:
- NXP Semiconductors
- Category:
- Power Management - Specialized
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MC34129DR2.pdf
- Description:
- IC CURRENT MODE CTRLR 14-SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,959
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Product details
Overview
MC34129DR2 from Freescale Semiconductor is a high-performance current-mode PWM controller IC designed for low-power digital telephone power supplies. It integrates a 2.5 V and 1.25 V bandgap reference, error amplifier with full pin access, soft-start buffer, fault timer, undervoltage lockout, and ±1.0 A totem-pole drive output - enabling direct MOSFET gate drive in flyback converters operating up to 300 kHz.
For engineers reviewing the MC34129DR2 datasheet, MC34129DR2 pinout, MC34129DR2 application, or MC34129DR2 equivalent, this page delivers verified technical context, SO-14 package mapping, real-world startup/lockout behavior, current-limiting architecture, and validated alternatives for telecom and isolated DC-DC designs.
Technical Context
The MC34129DR2 implements current-mode control via ramp input (Pin 3) synchronized with an internal sawtooth oscillator programmed by RT/CT (Pin 5), supporting frequencies from 80–120 kHz (typ.) and up to 300 kHz. Its latching PWM comparator ensures single-pulse-per-cycle operation, while cycle-by-cycle current limiting is enforced by clamping the feedback/PWM input (Pin 11) to 1.95 V during overload.
Startup uses a dedicated Start/Run comparator (Pin 13) with 2.0 V threshold and 350 mV hysteresis to enable bootstrap biasing; undervoltage lockout activates below 3.6 V (with 10% hysteresis) and holds Drive Output (Pin 1) low. The fault timer provides automatic recovery after ≥400 µs (typ.) of sustained overcurrent, discharging CSoft–Start (Pin 12) to initiate hiccup-mode restart.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 80–120 kHz typical (RT = 25.5 kΩ, CT = 390 pF); supports up to 300 kHz with external timing components |
| Drive Output Current | ±1.0 A peak sink/source capability - sufficient for direct gate drive of medium-power MOSFETs without external buffers |
| Reference Voltages | 1.25 V ±2% (bandgap, trimmed), 2.50 V ±5% (derived); used for error amp bias and CT charging |
| Soft-Start Clamp Voltage | 1.95 V internal clamp on Pin 11 - limits max peak switch current to (1.675 V)/RS during startup/fault |
| Fault Timer Delay | 200–600 µs timeout - triggers automatic soft-start restart under sustained overload or input collapse |
| Undervoltage Lockout | 3.6 V turn-on threshold with 350 mV hysteresis - prevents erratic operation during brownout or cold start |
| Operating Temperature | 0°C to +70°C ambient - qualified for commercial-grade telecom terminal applications |
Pinout & Package
MC34129DR2 is housed in a 14-pin SOIC (Small Outline Integrated Circuit) plastic package, case 751A, with gull-wing leads and standard JEDEC MS-012AC footprint. Thermal resistance θJA = 145°C/W at TA = 70°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Drive Output | ±1.0 A totem-pole stage directly drives MOSFET gate; fall time ≤30 ns (500 pF load) |
| 2 | Drive Ground | Dedicated power ground return - isolates switching noise from control circuitry ground (Pin 7) |
| 3 | Ramp Input | Current-sense input with 275 mV offset - terminates switch conduction when inductor current exceeds error signal |
| 4 | Sync/Inhibit Input | Accepts external clock for synchronization or DC voltage (2.0–VCC) to inhibit output |
| 5 | RT/CT | Timing node for oscillator frequency and deadtime programming via resistor-to-Vref2.5V and capacitor-to-GND |
| 6 | Vref 2.5 V | Stable 2.5 V output - sources charging current for CT through RT; ±5% tolerance at 25°C |
| 7 | Gnd | Control circuitry ground reference - separate from Drive Ground (Pin 2) for noise immunity |
| 8 | Vref 1.25 V | Precision 1.25 V bandgap reference - ±2% trimmed, used for error amp noninverting input (Pin 9) |
| 9 | Error Amp Noninverting Input | Connected to 1.25 V reference - sets regulation setpoint in feedback loop |
| 10 | Error Amp Inverting Input | Connected to output voltage divider - compares actual output against 1.25 V reference |
| 11 | Feedback/PWM Input | OR'd output of error amp and soft-start buffer - controls peak inductor current on cycle-by-cycle basis |
| 12 | CSoft–Start | Soft-start capacitor connection - 1.0 µA internal current charges CSS to 1.95 V for controlled startup |
| 13 | Start/Run Output | Open-collector output controlling external bootstrap transistor - switches off at 1.95 V to enable transformer-derived bias |
| 14 | VCC | Supply input (4.2–12 V range); includes 14.3 V zener clamp for gate protection during startup |
Key Features
| Feature | Design Value |
|---|---|
| Current-mode PWM control | Enables fast transient response and inherent cycle-by-cycle current limiting without slope compensation |
| Integrated fault timer with auto-restart | Prevents latch-up during input collapse (e.g., long twisted-pair telecom lines) via 400 µs (typ.) timeout and soft-start recycle |
| Bootstrap start/run comparator | Reduces system power loss by switching from external startup bias to auxiliary winding bias once regulation is achieved |
| Two precision references (1.25 V & 2.5 V) | 1.25 V ±2% reference enables accurate output regulation; 2.5 V ±5% reference powers oscillator timing network |
| High-current totem-pole driver | ±1.0 A drive strength eliminates need for external gate drivers in sub-10 W flyback designs |
Applications
| Telecom Line-Powered Terminal | Digital Phone Power Supply |
|---|---|
Use Scenario: Remote digital telephone derives operating power from POTS line via 20–48 V DC over twisted pair. IC Role / Device Role / Timing Role: MC34129DR2 acts as primary-side current-mode controller in non-isolated flyback, managing startup, regulation, and fault recovery under high-impedance source conditions. Use Value: Fault timer and soft-start ensure reliable cold-start from low-current line; ±1.0 A drive enables compact, low-component-count design. | Use Scenario: Wall-powered VoIP phone requires isolated ±5 V outputs for codec, processor, and interface circuits. IC Role / Device Role / Timing Role: MC34129DR2 serves as fixed-frequency current-mode controller in isolated flyback, coordinating sync input for EMI reduction and using dual references for precise feedback. Use Value: 1.25 V reference enables tight output regulation; Start/Run output manages auxiliary winding bias for >73% efficiency at full load. |
| Low-Power Industrial Flyback | Isolated Sensor Interface Supply |
Use Scenario: PLC I/O module needs 5 V/380 mA isolated supply from 24 VDC bus with minimal ripple and high line/load regulation. IC Role / Device Role / Timing Role: MC34129DR2 operates as primary-side controller with secondary-side optocoupler feedback, leveraging error amp access for loop compensation. Use Value: Full-access error amp (Pins 9, 10, 11) allows stable compensation across temperature; undervoltage lockout prevents brownout-induced reset. | Use Scenario: Isolated analog sensor node requires clean, low-noise 3.3 V supply derived from 12 V input with galvanic separation. IC Role / Device Role / Timing Role: MC34129DR2 configures as low-power flyback controller with adjustable deadtime (via RT/CT) to minimize cross-conduction losses in synchronous rectification. Use Value: Sync/Inhibit input allows external clock locking for EMI compliance; 2.5 V reference stabilizes timing network against supply variation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar current-mode PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC3842N | Fixed 52 kHz oscillator; no integrated fault timer or soft-start clamp; 1 A drive not guaranteed - typically ~0.5 A sink/source | Lacks auto-restart under line collapse; requires external soft-start circuit; less suited for telecom line-powered designs | Choose UC3842N only for cost-sensitive, fixed-frequency, non-telecom applications where fault recovery is handled externally |
| TL494CN | Dual-output PWM with built-in deadtime control; 200 mA drive per output; no dedicated ramp input or fault timer | Designed for push-pull/bridge topologies; lacks current-mode ramp interface and telecom-specific startup logic | Select TL494CN for dual-output or duty-cycle-limited topologies, not for single-switch current-mode flyback with line-impedance resilience |
Compared with UC3842N and TL494CN, MC34129DR2 uniquely combines telecom-optimized startup (bootstrap comparator), automatic fault recovery (integrated timer), and ±1.0 A drive in a single SO-14 package - making it irreplaceable for line-powered terminal power where input impedance and reliability under overload are critical.
Availability
MC34129DR2 is available at Aetrix Electronics and suitable for telecom terminal power supplies, isolated flyback converters, low-power industrial DC-DC modules, and sensor interface supplies requiring stable component supply and long-term manufacturability.
Supply support for MC34129DR2 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
Freescale Semiconductor (now part of NXP Semiconductors) is a global leader in analog and mixed-signal ICs, with deep expertise in power management, automotive, and industrial control solutions.
The MC34129DR2 belongs to Freescale's legacy analog controller product line, specifically engineered for low-power, high-reliability digital telephone power conversion - emphasizing fault resilience, startup efficiency, and integration for telecom infrastructure.
FAQ
What is the maximum oscillator frequency supported by MC34129DR2?
The MC34129DR2 supports oscillator frequencies up to 300 kHz using external RT/CT components. Typical operation is 80–120 kHz (with RT = 25.5 kΩ, CT = 390 pF), but higher frequencies are achievable with reduced timing capacitance and adjusted resistor values per Figure 1 in the datasheet. Operation beyond 300 kHz is not characterized or guaranteed.
Does MC34129DR2 include an internal soft-start function?
Yes, MC34129DR2 includes a dedicated soft-start function implemented via Pin 12 (CSoft–Start). An internal 1.0 µA current source charges an external capacitor to a 1.95 V clamp, controlling the ramp-up of peak inductor current. This prevents inrush current and ensures stable startup - especially critical in high-impedance telecom line-powered applications.
How does the fault timer in MC34129DR2 improve reliability in telecom applications?
The fault timer in MC34129DR2 detects sustained overcurrent or input voltage collapse (e.g., due to long twisted-pair impedance) and automatically discharges CSoft–Start after 200–600 µs, initiating a new soft-start cycle. This hiccup-mode recovery prevents thermal runaway and enables self-recovery without system-level intervention - a key reliability feature for unattended digital telephone terminals.
Can MC34129DR2 drive a MOSFET directly without an external gate driver?
Yes, MC34129DR2 features a ±1.0 A totem-pole output stage (Pin 1) optimized for direct MOSFET gate drive. With 30 ns typical fall time into 500 pF and robust sink/source capability, it eliminates the need for external drivers in sub-10 W flyback designs - confirmed by Figures 24 and 28 in the datasheet using MTP10N10M and SENSEFET devices.
What is the purpose of the Start/Run Output (Pin 13) in MC34129DR2?
The Start/Run Output (Pin 13) in MC34129DR2 controls an external bootstrap transistor to manage power sequencing: during startup, it enables bias from the input rail (Vin); once CSoft–Start reaches 1.95 V, it switches low to disable the transistor and transition to efficient auxiliary winding bias. This improves overall system efficiency in telecom power supplies.
MC34129DR2 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- -
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Applications:
- Telecommunications
- Current - Supply:
- 2.5mA
- Voltage - Supply:
- 4V ~ 12V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
MC34129DR2 FAQ
1.How can I place an order for MC34129DR2 through Aetrix?
Please submit a Request for Quotation (RFQ) for MC34129DR2 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 MC34129DR2 reliable?
The price and inventory of MC34129DR2 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC34129DR2 is usually 5 days.
3.What payment methods are accepted for MC34129DR2?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MC34129DR2 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MC34129DR2?
MC34129DR2 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC34129DR2 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 MC34129DR2?
For technical support, including MC34129DR2 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC34129DR2 requirements.
6.How does Aetrix verify that MC34129DR2 is sourced from the original manufacturer or authorized distributors?
All MC34129DR2 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 MC34129DR2 meets industry standards.
7.What is the process for return or replacement of MC34129DR2?
All MC34129DR2 units undergo pre-shipment inspection (PSI). If there is an issue with MC34129DR2, 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 MC34129DR2 part is unused and in its original packaging.
Return procedure for MC34129DR2:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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