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Document overview

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Technical content

Features

  • Ideal for 1.8V switching converters
  • Low-voltage operation: − 400mV maximum saturation over operating temperature range
  • Easy-to-use − Voltage in, current out
  • 2% voltage tolerance over operating temperature range

Applications

  • Optically-isolated, low-voltage power supplies
  • Low-voltage discrete regulator control Typical Application 200kHz DC-to-DC Flyback Converter Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com October 10, 2014 Revision 2.0

Micrel, Inc. MIC4043

Ordering Information

Part Number(1) Marking Voltage (V) Tolerance Configuration Temperature Range Package MIC4043YM4 RB1D 1.245 1% Open Collector –40°C to +85°C SOT-143 Note: 1. Underbar ( ) symbol may not be to scale. Pin Configuration SOT-143 (M4) (Top View) Pin Description Pin Number Pin Name Pin Function 1 IN Input: Supply voltage input. 2 SNK Sink (Output): NPN open collector output.

3 GND Ground

4 FB Feedback (Input): Feedback input from external voltage-divider network. October 10, 2014 2 Revision 2.0

Micrel, Inc. MIC4043 Absolute Maximum Ratings(2) ESD Rating(4) Operating Ratings(3) Electrical Characteristics(5) TA = +25°C, bold values indicate –40°C ≤ TA ≤ +85°C, unless noted. Parameter Condition Min. Typ. Max. Units Reference Voltage(5) 1.245 V Reference Voltage Tolerance Supply Current ISNK = 0mA 35 65 µA Transconductance (∆ISNK / ∆VIN) 1mA < ISNK < 15mA 3.5 150 S Output Transistor Saturation Voltage ISNK = 15mA 160 250 mV 400 Output Leakage VSNK = 5V, output transistor off 0.5 µA Notes: 2. Exceeding the absolute maximum ratings may damage the device. 3. The device is not guaranteed to function outside its operating ratings. 5. Reference voltage is not referenced to ground. The reference is between the IN and FB pins. October 10, 2014 3 Revision 2.0

Micrel, Inc. MIC4043 Test Circuit Test Circuit 1: Compensation (Bode Plot) Circuit Test Circuit 2: Transient Response Circuit October 10, 2014 4 Revision 2.0

Micrel, Inc. MIC4043 Functional Characteristics October 10, 2014 5 Revision 2.0

Micrel, Inc. MIC4043 Functional Diagram October 10, 2014 6 Revision 2.0

Micrel, Inc. MIC4043 Functional Description The MIC4043 combines a G M amplifier, precision 1.245V reference, and a pass transistor in a single package. The operation of the MIC4043 is similar to conventional shunt regulators such as the industry standard ’431. In a closed loop system, the MIC4043 maintains the desired feedback voltage at the FB pin by sinking current onto the SNK pin proportional to the error voltage at the FB pin. The ratio of sink current to error voltage is the transconductance of the device. Reference The MIC4043 uses a high- side reference. External voltage dividers providing feedback to the MIC4043 will be inverted when compared to those used with ’431- equivalent devices. Behavior The external feedback voltage is compared to the internal high-side 1.245V reference. If the feedback voltage, V FB, is less than V IN – VREF, the amplifier provides no drive to the sink transistor. If the feedback voltages are greater than V IN – VREF, the amplifier drives the pass transistor which sinks current to ground. October 10, 2014 7 Revision 2.0

Micrel, Inc. MIC4043 Package Information and Recommended Landing Pattern(6) SOT-143 (M4) Note: October 10, 2014 13 Revision 2.0

Micrel, Inc. MIC4043 MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com Micrel, Inc. is a leading global manufacturer of IC solutions for the worldwide high performance linear and power, LAN, and t iming & communications markets. The Company’s products include advanced mixed -signal, analog & power semiconductors; high- performance communication, clock management, MEMs-based clock oscillators & crystal -less clock generators, Ethernet switches, and physical layer transceiver ICs. Company customers include leading manufacturers of enterprise, co nsumer, industrial, mobile, telecommunications, automotive, and computer products. Corporation headquarters and state -of-the-art wafer fabrication facilities are located in San Jose, CA, with regional sales and support offices and advanced technology design centers situated throughout the Americas, Europe, and Asia. Additionally, the Company maintains an extensive network of distributors and reps worldwide. Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry, specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual property rights is granted by this document. E xcept as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or wa rranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright, or other intellectual property right. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where mal function of a product can reasonably be expected to result in personal injury. Life support devices or syste ms are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2000 Micrel, Incorporated. October 10, 2014 14 Revision 2.0