MIC37100/37101/ General Description. Features. Applications. Typical Applications. 1A Low-Voltage µcap LDO Regulator

Transcription

1 MIC37/37/37 MIC37/37/37 A Low-Voltage µcap LDO Regulator General Description The MIC37, MIC37, and MIC37 are A low-dropout, linear voltage regulators that provide low-voltage, high-current output from an extremely small package. Utilizing s proprietary Super βeta PNP pass element, the MIC37// offers extremely low dropout (typically 8mV at A) and low ground current (typically ma at A). The MIC37 is a fixed output regulator offered in the SOT-3 package. The MIC37 and MIC37 are fixed and adjustable regulators, respectively, in a thermally enhanced power 8-lead SOIC (small outline package) and the SOT-3 package. The MIC37 is also available in the S- PAK power package, for applications that require higher power dissipation or higher operating ambient temperatures. The MIC37// is ideal for PC add-in cards that need to convert from standard V to 3.3V, 3.3V to.v or.v to.8v or lower. A guaranteed maximum dropout voltage of mv over all operating conditions allows the MIC37// to provide.v from a supply as low as 3V and.8v from a supply as low as.3v. The MIC37// is fully protected with overcurrent limiting and thermal shutdown. Fixed output voltages of.v,.6v,.8v,.v and 3.3V are available on MIC37/ with adjustable output voltages to.4v on MIC37. For other voltages, contact. All support documentation can be found on s web site at Features Fixed and adjustable output voltages to.4v µcap Regulator, µf ceramic output capacitor stable 8mV typical dropout at A Ideal for 3.V to.v conversion Ideal for.v to.8v,.6v or.v conversion A minimum guaranteed output current % initial accuracy Low ground current Current limiting and thermal shutdown Reversed-leakage protection Fast transient response Low-profile SOT-3 package Power SO-8 package S-PAK package (MIC37 only) Applications LDO linear regulator for PC add-in cards PowerPC power supplies High-efficiency linear power supplies SMPS post regulator Multimedia and PC processor supplies Battery chargers Low-voltage microcontrollers and digital logic Typical Applications V IN 3.3V MIC37 IN.V 3 3 Dropout vs. Output Current.V.V/A Regulator µf ceramic DROP (mv) 3.3V...7 PUT CURRENT (A) Super βeta PNP is a registered trademark of, Inc. PowerPC is a trademark of IBM Corporation., Inc. 8 Fortune Drive San Jose, CA 93 USA tel + (48) fax + (48) September M

2 MIC37/37/37 Ordering Information Part Number Voltage Junction Temp. Range Package Standard Pb-Free MIC37-.BS MIC37-.WS*.V -4 C to + C SOT-3 MIC37-.6BS MIC37-.6WS*.6V -4 C to + C SOT-3 MIC37-.8BS MIC37-.8WS*.8V -4 C to + C SOT-3 MIC37-.BS MIC37-.WS*.V -4 C to + C SOT-3 MIC37-3.3BS MIC37-3.3WS* 3.3V -4 C to + C SOT-3 MIC37-.BM MIC37-.YM.V -4 C to + C SOIC-8 MIC37-.6BM MIC37-.6YM.6V -4 C to + C SOIC-8 MIC37-.8BM MIC37-.8YM.8V -4 C to + C SOIC-8 Contact Factory MIC37-.YM. V -4 C to + C SOIC-8 MIC37-.BM MIC37-.YM.V -4 C to + C SOIC-8 MIC37-3.3BM MIC37-3.3YM 3.3V -4 C to + C SOIC-8 MIC37BM MIC37YM Adj. -4 C to + C SOIC-8 MIC37BR MIC37WR* Adj. -4 C to + C S-PAK- * Pb-Free RoHS compliant with high-melting solder exemption. Pin Configuration TAB 3 IN MIC37-x.x (Fixed) SOT-3 (S) TAB ADJ 4 3 IN EN MIC37 (Adjustable) S-PAK- (R) EN 8 EN 8 IN 7 IN FLG 4 ADJ 4 MIC37-x.x (Fixed) SOIC-8 (M) MIC37 (Adjustable) SOIC-8 (M) M September

3 MIC37/37/37 Pin Description Pin No. Pin No. Pin No. Pin No. Pin Name Pin Function MIC37 MIC37 MIC37 MIC37 SOT-3 SOIC-8 SOIC-8 S-PAK EN Enable (Input): CMOS-compatible control input. Logic high = enable, logic low or open = shutdown. IN Supply (Input) Regulator Output. 4 FLG Flag (Output): Open-collector error flag output. Active low = output under voltage. 4 ADJ Adjustment Input: Feedback input. Connect to resistive voltage-divider network., TAB 8 8 3, TAB Ground. September 3 M

4 MIC37/37/37 Absolute Maximum Ratings () Supply Voltage (V IN )...V to +6.V Enable Voltage (V EN )...+6.V Storage Temperature (T S )... 6 C to + C Lead Temperature (soldering, sec.)... 6 C ESD... (3) Operating Ratings () Supply Voltage (V IN )... +.V to +6V Enable Voltage (V EN )...V to +6V Maximum Power Dissipation (P D(max) )... (4) Junction Temperature (T J )... 4 C to + C Package Thermal Resistance SOT-3 (θ JC )... C/W SOIC-8 (θ JC )... C/W S-PAK- (θ JC )... C/W Electrical Characteristics V IN = V + V; V EN =.V; T J = C, bold values indicate 4 C T J + C; unless noted Symbol Parameter Condition Min Typ Max Units V Output Voltage ma % ma I A, V + V V IN 6V % Line Regulation I = ma, V + V V IN 6V.6. % Load Regulation V IN = V + V, ma I A,. % ΔV /ΔT Output Voltage Temp. Coefficient (6) 4 pm/ C V DO Dropout Voltage (6) I = ma, ΔV = % mv I = ma, ΔV = % 3 mv I = 7mA, ΔV = % 4 mv I = A, ΔV = % 8 mv I (7) I = ma, V IN = V + V 6 µa I = ma, V IN = V + V 3. ma I = 7mA, V IN = V + V 6.7 ma I = A, V IN = V + V ma I (lim) Current Limit V = V, V IN = V + V.6. A Enable Input V EN Enable Input Voltage logic low (off).8 V logic high (on). V I EN Enable Input Current V EN =.V 3 µa Flag Output V EN =.8V µa 4 µa I FLG(leak) Output Leakage Current V OH = 6V. µa µa V FLG(do) Output Low Voltage V IN =.V, I OL, = µa mv V FLG Low Threshold % of V 93 % High Threshold % of V 99. % Hysteresis % M September

5 MIC37/37/37 Symbol Parameter Condition Min Typ Max Units MIC37 Only Notes: Reference Voltage.8.4. V..6 V Adjust Pin Bias Current 4 8 na na. Exceeding the absolute maximum ratings may damage the device.. The device is not guaranteed to function outside its operating rating. 3. Devices are ESD sensitive. Handling precautions recommended. 4. P D (max) = (T J (max) T A ) θ JA, where θ JA depends upon the printed circuit layout. See Applications Information section.. Output voltage temperature coefficient is ΔV (worst case) (T J (max) T J (min)) where T J (max) is + C and T J (min) is 4 C. 6. V DO = V IN V when V decreases to 98% of its nominal output voltage with V IN = V + V. For output voltages below.v, dropout voltage is the input-to-output voltage differential with the minimum input voltage being.v. Minimum input operating voltage is.v. 7. I is the quiescent current. I IN = I + I. 8. V EN.8V, V IN 6V, and V = V. September M

6 MIC37/37/37 Typical Characteristics PSRR (db) Power Supply Rejection Ratio I = ma C = F C IN = V IN = V V = 3.3V.. FREQUENCY (KHz) PSRR (db) Power Supply Rejection Ratio V IN = V V = 3.3V 3 I = ma C = 47 F C IN =.. FREQUENCY (KHz) PSRR (db) Power Supply Rejection Ratio V IN = 3.3V V =.V 3 I = ma C = F C IN =.. FREQUENCY (KHz) PSRR (db) Power Supply Rejection Ratio V IN = 3.3V V =.V 3 I = ma C = 47 F C IN =.. FREQUENCY (KHz) DROP (mv) 3 3 Dropout vs. Output Current.V 3.3V...7 PUT CURRENT (A) DROP (mv) Dropout.V PUT VOLTAGE (V) Dropout Characteristics (.V) ma Load ma Load PUT VOLTAGE (V) Dropout Characteristics (.8V) ma Load ma Load PUT VOLTAGE (V) Dropout Characteristics (.V) ma Load ma Load PUT VOLTAGE (V) Dropout Characteristics (3.3V) ma Load ma Load vs. Output Current 4.V 3.3V...7 PUT CURRENT (A) vs. Supply Voltage (.V) ma ma M September

7 MIC37/37/ vs. Supply Voltage (.V) ma 7mA vs. Supply Voltage (.8V) ma ma vs. Supply Voltage (.8V) ma 7mA vs. Supply Voltage (.V) ma. ma vs. Supply Voltage (.V) ma 7mA vs. Supply Voltage (3.3V) ma ma vs. Supply Voltage (3.3V) 7mA ma V. I =ma V. I =ma V I =ma PUT VOLTAGE (V) Output Voltage.V SHORT CIRCUIT CURRENT (A) Short Circuit Current vs. Supply Voltage SUPPLY VOLTAGE (V) September 7 M

8 MIC37/37/37 SHORT CIRCUIT CURRENT (A) Short Circuit Current.V IN FLAG VOLTAGE (V) Flag Voltage vs. Flag Current 3.3V IN V IN.V IN FLAG CURRENT (ma) FLAG LOW VOLTAGE (mv) 3 3 Flag Low Voltage Flag Current = A FLAG VOLTAGE (V) Error Flag Pull-Up Resistor 6 Flag High (OK) V =V IN 4 3 Flag Low (FAULT).. RESISTANCE (k ) ENABLE CURRENT ( A) Enable Current.V EN M September

9 MIC37/37/37 Functional Characteristics Load Transient Response Load Transient Response PUT VOLTAGE (mv/div) V IN = 3.3V V =.V C = µf Ceramic PUT VOLTAGE (mv/div) V IN = 3.3V V =.V C = µf Ceramic ma ma LOAD CURRENT (ma/div) ma LOAD CURRENT (ma/div) ma TIME (4µs/div.) TIME (4s/div.) Line Transient Response Enable Transient Response INPUT VOLTAGE (V/div) PUT VOLTAGE (mv/div) V 3.3V V =.V C = µf Ceramic Load=mA ENABLE VOLTAGE (V/div) PUT VOLTAGE (V/div) V IN = 3.3V V =.V I = ma C = µf Ceramic TIME (4µs/div.) TIME (µs/div.) September 9 M

10 MIC37/37/37 Functional Diagrams IN Ref..4V Thermal Shutdown MIC37 MIC37 Fixed Regulator Block Diagram IN FLAG.8V Ref..4V EN Thermal Shutdown MIC37 MIC37 Fixed Regulator with Flag and Enable Block Diagram IN Ref..4V EN ADJ Thermal Shutdown MIC37 MIC37 Adjustable Regulator Block Diagram M September

11 MIC37/37/37 Applications Information The MIC37// is a high-performance low-dropout voltage regulator suitable for moderate to high-current voltage regulator applications. Its mv dropout voltage at full load and overtemperature makes it especially valuable in battery-powered systems and as high-efficiency noise filters in post-regulator applications. Unlike older NPN-pass transistor designs, where the minimum dropout voltage is limited by the base-to-emitter voltage drop and collector-to-emitter saturation voltage, dropout performance of the PNP output of these devices is limited only by the low V CE saturation voltage. A trade-off for the low dropout voltage is a varying base drive requirement. s Super βeta PNP process reduces this drive requirement to only % of the load current. The MIC37// regulator is fully protected from damage due to fault conditions. Linear current limiting is provided. Output current during overload conditions is constant. Thermal shutdown disables the device when the die temperature exceeds the maximum safe operating temperature. The output structure of these regulators allows voltages in excess of the desired output voltage to be applied without reverse current flow. V IN Output Capacitor C IN MIC37-x.x IN V C Figure. Capacitor Requirements The MIC37// requires an output capacitor to maintain stability and improve transient response. As a µcap LDO, the MIC37// can operate with ceramic output capacitors as long as the amount of capacitance is µf or greater. For values of output capacitance lower than µf, the recommended ESR range is mω to Ω. The minimum value of output capacitance recommended for the MIC37// is 4.7µF. For µf or greater the ESR range recommended is less than Ω. Ultra-low ESR ceramic capacitors are recommended for output capacitance of µf or greater to help improve transient response and noise reduction at high frequency. X7R/XR dielectric-type ceramic capacitors are recommended because of their temperature performance. X7R-type capacitors change capacitance by % over their operating temperature range and are the most stable type of ceramic capacitors. ZU and YV dielectric capacitors change value by as much as % and 6% respectively over their operating temperature ranges. To use a ceramic chip capacitor with YV dielectric, the value must be much higher than an X7R ceramic capacitor to ensure the same minimum capacitance over the equivalent operating temperature range. Input Capacitor An input capacitor of µf or greater is recommended when the device is more than 4 inches away from the bulk ac supply capacitance or when the supply is a battery. Small, surface mount, ceramic chip capacitors can be used for bypassing. Larger values will help to improve ripple rejection by bypassing the input to the regulator, further improving the integrity of the output voltage. Error Flag The MIC37 features an error flag (FLG), which monitors the output voltage and signals an error condition when this voltage drops % below its expected value. The error flag is an open-collector output that pulls low under fault conditions and may sink up to ma. Low output voltage signifies a number of possible problems, including an overcurrent fault (the device is in current limit) or low input voltage. The flag output is inoperative during overtemperature conditions. A pull-up resistor from FLG to either V IN or V is required for proper operation. For information regarding the minimum and maximum values of pull-up resistance, refer to the graph in the Typical Characteristics section of the data sheet. Enable Input The MIC37 and MIC37 versions feature an active-high enable input (EN) that allows on-off control of the regulator. Current drain reduces to zero when the device is shutdown, with only microamperes of leakage current. The EN input has TTL/CMOS compatible thresholds for simple logic interfacing. EN may be directly tied to V IN and pulled up to the maximum supply voltage Transient Response and 3.3V to.v or.v to.8v,.6v or.v Conversion The MIC37// has excellent transient response to variations in input voltage and load current. The device has been designed to respond quickly to load current variations and input voltage variations. Large output capacitors are not required to obtain this performance. A standard µf output capacitor, is all that is required. Larger values help to improve performance even further. By virtue of its low-dropout voltage, this device does not saturate into dropout as readily as similar NPN-based designs. When converting from 3.3V to.v or.v to.8v, or lower, the NPN based regulators are already operating in dropout, with typical dropout requirements of.v or greater. To convert down to.v or.8v without operating in dropout, NPN-based regulators require an input voltage of 3.7V at the very least. The MIC37 regulator will provide excellent performance with an input as low as 3.V or.v respectively. This gives the PNP based regulators a distinct advantage over older, NPN based linear regulators. September M

12 MIC37/37/37 Minimum Load Current The MIC37// regulator is specified between finite loads. If the output current is too small, leakage currents dominate and the output voltage rises. A ma minimum load current is necessary for proper regulation. Adjustable Regulator Design ENABLE SHUTDOWN V IN MIC37 IN EN ADJ R R C V Thermal resistance consists of two main elements, θ JC (junction-to-case thermal resistance) and θ CA (case-to-ambient thermal resistance). See Figure 3. θ JC is the resistance from the die to the leads of the package. θ CA is the resistance from the leads to the ambient air and it includes θ CS (caseto-sink thermal resistance) and θ SA (sink-to-ambient thermal resistance). SOIC-8 V.4V R R Figure. Adjustable Regulator with Resistors The MIC37 allows programming the output voltage anywhere between.4v and the 6V maximum operating rating of the family. Two resistors are used. Resistors can be quite large, up to MΩ, because of the very high input impedance and low bias current of the sense comparator: The resistor values are calculated by: R R V.4 Where V O is the desired output voltage. Figure shows component definition. Applications with widely varying load currents may scale the resistors to draw the minimum load current required for proper operation (see above). Power SOIC-8 Thermal Characteristics One of the secrets of the MIC37/ s performance is its power SO-8 package featuring half the thermal resistance of a standard SO-8 package. Lower thermal resistance means more output current or higher input voltage for a given package size. Lower thermal resistance is achieved by joining the four ground leads with the die attach paddle to create a singlepiece electrical and thermal conductor. This concept has been used by MOSFET manufacturers for years, proving very reliable and cost effective for the user. JC JA CA printed circuit board AMBIENT ground plane heat sink area Figure 3. Thermal Resistance Using the power SOIC-8 reduces the θ JC dramatically and allows the user to reduce θ CA. The total thermal resistance, θ JA (junction-to-ambient thermal resistance) is the limiting factor in calculating the maximum power dissipation capability of the device. Typically, the power SOIC-8 has a θ JC of C/W, this is significantly lower than the standard SOIC-8 which is typically 7 C/W. θ CA is reduced because pins through 8 can now be soldered directly to a ground plane which significantly reduces the case-to-sink thermal resistance and sink to ambient thermal resistance. Low-dropout linear regulators from are rated to a maximum junction temperature of C. It is important not to exceed this maximum junction temperature during operation of the device. To prevent this maximum junction temperature from being exceeded, the appropriate ground plane heat sink must be used. M September

13 MIC37/37/37 COPPER AREA (mm ) T J A = 4 C C C 6 C 7 C 8 C C POWER DISSIPATION (W) Figure 4. Copper Area vs. Power SO-8 Power Dissipation Figure 4 shows copper area versus power dissipation with each trace corresponding to a different temperature rise above ambient. From these curves, the minimum area of copper necessary for the part to operate safely can be determined. The maximum allowable temperature rise must be calculated to determine operation along which curve. ΔT = T J (max) T A (max) T J (max) = C T A (max) = maximum ambient operating temperature For example, the maximum ambient temperature is C, the ΔT is determined as follows: ΔT = C C ΔT = 7 C Using Figure 4, the minimum amount of required copper can be determined based on the required power dissipation. Power dissipation in a linear regulator is calculated as follows: P D = (V IN V ) I + V IN I If we use a.v output device and a 3.3V input at an output current of A, then our power dissipation is as follows: P D = (3.3V.V) A + 3.3V ma P D = 8mW + 36mW P D = 836mW From Figure 4, the minimum amount of copper required to operate this application at a ΔT of 7 C is 6mm. Quick Method Determine the power dissipation requirements for the design along with the maximum ambient temperature at which the device will be operated. Refer to Figure, which shows safe operating curves for three different ambient temperatures: C, C and 8 C. From these curves, the minimum amount of copper can be determined by knowing the maximum power dissipation required. If the maximum ambient temperature is C and the power dissipation is as above, 836mW, the curve in Figure shows that the required area of copper is 6mm. The θ JA of this package is ideally 63 C/W, but it will vary depending upon the availability of copper ground plane to which it is attached. COPPER AREA (mm ) T J = C T A = 8 C C C POWER DISSIPATION (W) Figure. Copper Area vs. Power-SOIC Power Dissipation September 3 M

14 MIC37/37/37 Package Information 3. (.4).9 (.4) C L C L 3.7 (.46) 7.49 (.9) 3.3 (.3) 6.7 (.64).4 (.9). (.87) 4.7 (.8) 4. (.77). (.4). (.8) 6.7 (.64) 6.3 (.48).4 (.4).8 (.33).7 (.67) 6. (.6) MAX DIMENSIONS: MM (INCH).38 (.). (.).84 (.33).64 (.).9 (.36) MI N SOT-3 (S) 8-Lead SOIC (M) M September

15 MIC37/37/37 Lead S-PAK (R) MICREL INC. 8 FORTUNE DRIVE SAN JOSE, CA 93 USA TEL + (48) FAX + (48) 474- WEB This information furnished by reserves the right to change circuitry and specifications at any time without notification to the customer. Products are not reasonably be expected to result in personal injury. Life support devices or systems 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 Pr for any damages resulting from such use or sale. Incorporated September M