Electronic Components Datasheet Search |
|
MIIC5271 Datasheet(PDF) 8 Page - Micrel Semiconductor |
|
MIIC5271 Datasheet(HTML) 8 Page - Micrel Semiconductor |
8 / 10 page MIC5271 Micrel MIC5271 8 October 2003 Applications Information The MIC5271 is a general-purpose negative regulator that can be used in any system that requires a clean negative voltage from a negative output. This includes post regulating of DC-DC converters (transformer based or charge pump based voltage converters). These negative voltages typically require a negative low dropout voltage regulator to provide a clean output from typically noisy lines. Input Capacitor A 1µF input capacitor should be placed from IN to GND if there is more than 2 inches of wire or trace between the input and the AC filter capacitor, or if a battery is used as the input. Output Capacitor The MIC5271 requires an output capacitor for stable opera- tion. A minimum of 1µF of output capacitance is required. The output capacitor can be increased without limitation to im- prove transient response. The output does not require ESR to maintain stability, therefore a ceramic capacitor can be used. High-ESR capacitors may cause instability. Capacitors with an ESR of 3Ω or greater at 100kHz may cause a high frequency oscillation. Low-ESR tantalums are recommended due to the tight ca- pacitance tolerance over temperature. Ceramic chip capacitors have a much greater dependence on temperature, depending upon the dielectric. The X7R is recommended for ceramic capacitors because the dielectric will change capacitance value by approximately 15% over temperature. The Z5U dielectric can change capacitance value by as much 50% over temperature, and the Y5V dielectric can change capacitance value by as much as 60% over temperature. To use a ceramic chip capacitor with the Y5V dielectric, the value must be much higher than a tanta- lum to ensure the same minimum capacitor value over temperature. No-Load Stability The MIC5271 does not require a load for stability. Enable Input The MIC5271 comes with an enable pin that allows the regulator to be disabled. Forcing the enable pin higher than the negative threshold and lower than the positive threshold disables the regulator and sends it into a “zero” off-mode current state. In this state, current consumed by the regulator goes nearly to zero. The MIC5271 will be in the on mode when the voltage applied to the enable pin is either greater than the positive threshold or less than the negative threshold. -5 -4 -3 -2 -1 0 1 2 3 4 5 -3 -5 -7 -9 -11 -13 -15 SUPPLY VOLTAGE (V) Enable Input Regulator On Regulator On Regulator Off Thermal Considerations Absolute values will be used for thermal calculations to clarify the meaning of power dissipation and voltage drops across the part. Proper thermal design for the MIC5271-5.0BM5 can be accomplished with some basic design criteria and some simple equations. The following information must be known to implement your regulator design: V IN = input voltage V OUT = output voltage I OUT = output current T A = ambient operating temperature I GND = ground current Maximum power dissipation can be determined by knowing the ambient temperature, T A, the maximum junction tem- perature, 125°C, and the thermal resistance, junction to ambient. The thermal resistance for this part, assuming a minimum footprint board layout, is 235°C/W. The maximum power dissipation at an ambient temperature of 25°C can be determined with the following equation: P TT D(max) J(max) A JA = − θ P 125 C 25 C 235 C/W D(max) = ° − ° ° P 425mW D(max) = The actual power dissipation of the regulator circuit can be determined using one simple equation. P D = (VIN – VOUT)IOUT + VIN × IGND Substituting P D(max), determined above, for PD and solving for the operating conditions that are critical to the application will give the maximum operating conditions for the regulator circuit. The maximum power dissipation number cannot be exceeded for proper operation of the device. The maximum input voltage can be determined using the output voltage of 5.0V and an output current of 100mA. Ground current, of 1mA for 100mA of output current, can be taken from the “ Electrical Characteristics ” section of the data sheet. 425mW V 5.0V 100mA V 1mA IN IN = − () +× 425mW 100mA V 1mA V 500mW IN IN =× + × () − 925mW 101mA V IN =× V 9.16Vmax IN = Therefore, a –5.0V application at 100mA of output current can accept a maximum input voltage of –9.16V in a SOT-23-5 package. For a full discussion of heat sinking and thermal effects on voltage regulators, refer to Regulator Thermals section of Micrel’s “Designing with Low Dropout Voltage Regulators” handbook. |
Similar Part No. - MIIC5271 |
|
Similar Description - MIIC5271 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |