MIC2171 Micrel Semiconductor, MIC2171 Datasheet
MIC2171
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MIC2171 Summary of contents
Page 1
... Cuk configurations as well as isolated topologies. Operating from 3V to 40V, the MIC2171 draws only 7mA of quiescent current, making it attractive for battery operated supplies. The MIC2171 is available in a 5-pin TO-220 or TO-263 for – +85 C operation. Typical Applications +5V (4.75V min.) ...
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... MIC2171 Ordering Information Part Number MIC2171BT MIC2171BU Pin Configuration Tab GND 5-lead TO-220 (BT) Pin Description Pin Number Pin Name 1 COMP GND Temperature Range – +85 C – + GND COMP Pin Function Frequency Compensation: Output of transconductance-type error amplifier. ...
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... MIC2171 Absolute Maximum Ratings Input Voltage (V ) ........................................................ 40V IN Switch Voltage (V ) .................................................... 65V SW Feedback Voltage (transient, 1ms) (V Operating Temperature Range ...................... –40 to +85 C Electrical Characteristics bold values indicate – Parameter Conditions Reference Section Feedback Voltage ( COMP Feedback Voltage 3V Line Regulation V COMP ...
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... MIC2171 Typical Performance Characteristics Minimum Operating Voltage 2.9 2.8 2.7 2.6 Switch Current = 2A 2.5 2.4 2.3 -100 - 100 150 Temperature ( C) Supply Current D. D. Operating Voltage (V) IN Switch On-Voltage 1.6 1 1.2 1 –40 C 0.8 0 125 C 0.4 0 Switch Current (A) Error Amplifier Gain 5 ...
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... Anti-Saturation The anti-saturation diode (D1) increases the usable duty cycle range of the MIC2171 by eliminating the base to collector stored charge which would delay Q1’s turnoff. Compensation Loop stability compensation of the MIC2171 can be accom- ...
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... Note: Input and output C2 R2 Figure 4. Current Limit The maximum current limit of the MIC2171 can be reduced by adding a voltage clamp to the COMP output (Figure 4). This feature can be useful in applications requiring either a com- plete shutdown of Q1’s switching action or a form of current fold-back limiting. This use of the COMP output does not disable the oscillator, amplifiers or other circuitry, therefore the supply current is never less than approximately 5mA ...
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... When L1 discharges its current completely during the MIC2171 off-time operating in discontinuous mode operating in continuous mode if it does not discharge completely before the MIC2171 power switch is turned on again. Discontinuous Mode Design Given the maximum output current, solve equation (1) to determine whether the device can operate in discontinuous mode without initiating the internal device current limit ...
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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 MIC2171 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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... MIC2171 IN(min) ON (10) L PRI P OUT Where maximum primary inductance PRI f = device switching frequency (100kHz minimum input voltage IN(min power switch on time ON Then 3.22 L PRI 2.5 L 11.4 H PRI Use primary inductance to overcome circuit ineffi- ciencies. To complete the design the inductance value of the second- ...
Page 10
... To prevent core saturation, the application given here uses a duty cycle limiter consisting of Q1, C4 and R3. Whenever the MIC2171 exceeds a duty cycle of 50%, T1’s reset winding current turns Q1 on. This action reduces the duty cycle of the MIC2171 until T1 is able to reset during each cycle. ...