mic3172 Micrel Semiconductor, mic3172 Datasheet
mic3172
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mic3172 Summary of contents
Page 1
... Operating from 3V to 40V, the MIC2172/3172 draws only 7mA of quiescent current making it attractive for battery operated supplies. The MIC3172 is for applications that require on/off control of the regulator. The MIC3172 is externally shutdown by applying a TTL low signal to EN (enable). When disabled, the MIC3172 draws only leakage current (typically less than 1µ ...
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... FB 3 *SYNC/ † 8-pin DIP (N) Pin Description Pin Number Pin Name 1 S GND 2 COMP (MIC2172) SYNC 4 (MIC3172 GND GND 1 M9999-042205 Part Number Temperature Pb-Free Range MIC2172YN –40°C to +85°C MIC2172YM –40°C to +85°C MIC3172YN – ...
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MIC2172/3172 Absolute Maximum Ratings MIC2172 Input Voltage ................................................................. 40V Switch Voltage .............................................................. 65V Sync Current .............................................................. 50mA Feedback Voltage (Transient, 1ms) ........................... ±15V Operating Temperature Range 8-pin PDIP ................................................. –40 to +85°C 8-pin SOIC ................................................ –40 to +85°C Electrical Characteristics ...
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... Micrel, Inc. Min Typ Max Units 88 100 112 85 115 120 2.2 4 2.7 3 0.833 (2-δ) for the MIC3172 5V. IN Min Typ Max Units 1.224 1.240 1.264 1.214 1.274 0.07 310 750 1100 April 2005 kHz kHz % %/V ...
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... MIC3172. CL M9999-042205 V/V µA µ Ω Ω kHz kHz % V mA µ µA µA ...
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... Feedback Voltage Line Regulation 125° 25° -40° Operating (V) IN Enable Thresholds 1.4 MIC3172 1.3 ON 1.2 1.1 OFF 1 0.9 0.8 -100 - 100 150 Temperature (°C) Current Limit 4 3 –40°C 25°C 2 125° ...
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MIC2172/3172 Typical Performance Characteristics Error Amplifier Gain 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -100 - 100 150 Temperature (°C) Block Diagram MIC2172 SYNC Pin 4 FB ...
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... The MIC2172/3172 operates when V 2.0V for the MIC3172). An internal 2.3V regulator supplies biasing to all internal circuitry including a precision 1.24V band gap reference. The enable control (MIC3172 only) enables or disables the internal regulator which supplies power to all other internal circuitry. PWM Operation The 100kHz oscillator generates a signal with a duty cycle of approximately 90% ...
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... Logic Gate Figure 5. Adapting to the LT1172 Socket April 2005 By using the MIC3172, U1 and Q1 shown in figure 5 can be eliminated, reducing the total components count. Synchronizing the MIC2172 Using several unsynchronized switching regulators in the same circuit will cause beat frequencies to appear on the inputs and outputs. These beat frequencies can be very low making them difficult to filter. Micrel’ ...
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MIC2172/3172 Figure 7 shows how one or more MIC2172s can be locked to an external reference frequency. The slaves lock to the negative (falling edge) of the external reference waveform. Soft Start A diode-coupled capacitor from COMP to circuit ground ...
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... GND Single point ground * MIC3172 only Figure 10. Single Point Ground A single point ground is strongly recommended for proper operation. The signal ground, compensation network ground, and feed- back network connections are sensitive to minor voltage variations. The input and output capacitor grounds and power ground conductors will exhibit voltage drop when carrying large currents ...
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... C4 may provide satisfactory output ripple volt- age making additional filter stages unnecessary. C1 (input capacitor) may be reduced or eliminated if the MIC3172 is located near a low impedance voltage source. Output Diode The output diode allows T1 to store energy in its primary inductance (D2 nonconducting) and release energy into C4 (D2 conducting) ...
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... R4* C3* 22µF D1 1:1. 100µH MIC3172 PRI COMP FB GND 1µF Figure 12. MIC3172 5V 0.25A Flyback Converter 0 IN(min ≤ PRI P OUT = maximum primary inductance PRI = device switching frequency (100kHz minimum input voltage IN(min) = power switch on time ...
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... Micrel’s MIC2172/3172 can be used in several circuit con- figurations to generate an output voltage which is less than the input voltage (buck or step-down topology). Figure 13 shows the MIC3172 in a voltage step-down application. Because of the internal architecture of these devices, more external components are required to implement a step-down regulator than with other devices offered by Micrel (refer to the LM257x or LM457x family of buck switchers) ...
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... D3. During the positive half cycle, lamp current is rectified by D2 through R4 and R5. R3 and C5 filter the voltage dropped across R4 and R5 to the MIC3172’s feedback pin. The MIC3172 maintains a constant lamp current by adjusting its duty cycle to keep the feedback voltage at 1 ...
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... MIC2172/3172 On/Off Control Especially important for battery powered applications, the lamp can be remotely or automatically turned off using the MIC3172’s EN pin. The entire circuit draws less than 1µA while shutdown 4.5V to 20V Enable (On) Shutdown (Off) Figure 15. LCD Backlight Fluorescent Lamp Supply ...
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MIC2172/3172 Package Information 0.018 (0.57) 0.026 (0.65) 0.157 (3.99) 0.150 (3.81) 0.064 (1.63) 0.045 (1.14) MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA + 1 (408) 944-0800 TEL This information furnished by Micrel in this data sheet is ...