MIC5249 Micrel MIC5249 300mA µCap LDO with Programmable Power-On Reset Delay General Description Features The MIC5249 is an efficient, precise 300mA CMOS voltage regulator with power-on reset delay which can be implemented via an external capacitor. It offers 1% initial accuracy, extremely-low-dropout voltage (typically 400mV @ 300mA), and low ground current (typically 85mA) over load. Designed specifically for noise-critical applications in handheld or battery-powered devices, the MIC5249 comes equipped with a noise reduction feature to filter the output noise via an external capacitor. Other features of the MIC5249 include a logic compatible enable pin, current limit, thermal shutdown, ultra-fast transient response, and an active clamp to speed up device turnoff. The MIC5249 also works with low-ESR ceramic capacitors, reducing the amount of board space necessary for power applications, critical in hand-held wireless devices. The MIC5249 is available in the MSOP-8 package. All support documentation can be found on Micrel’s web site at www.micrel.com. • • • • • 300mA output current High PSRR: 65dB@120Hz Stable with ceramic output capacitor Power-on RESET output with adjustable delay time High output accuracy: ±1.0% initial accuracy ±3.0% over temperature Low dropout voltage of 400mV @ 300mA Low quiescent current: 85µA Zero current shutdown mode Thermal shutdown protection Current-limit protection Tiny MSOP-8 package • • • • • • Applications • Cellular phones • PDAs • Fiber optic modules Ordering Information Part Number Voltage* Junction Temp. Range Package MIC5249-1.8BMM 1.8V –40°C to 125°C MSOP-8 MIC5249-2.5BMM 2.5V –40°C to 125°C MSOP-8 MIC5249-2.6BMM 2.6V –40°C to 125°C MSOP-8 MIC5249-2.8BMM 2.8V –40°C to 125°C MSOP-8 MIC5249-2.85BMM 2.85V –40°C to 125°C MSOP-8 MIC5249-3.0BMM 3.0V –40°C to 125°C MSOP-8 * Other voltages available. Contact Micrel for details. Typical Application MIC5249-x.xBMM VIN IN ENABLE SHUTDOWN VOUT OUT EN RESET RESET DELAY CBYP GND CAD=1.0µF Ceramic Sets the delay for the RESET output COUT=2.2µF Ceramic CBYP=0.01µF Ultra-Low-Noise Application Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com March 2004 1 M0382-033004 MIC5249 Micrel Pin Configuration CBYP 1 8 ENABLE DELAY 2 7 RESET GND 3 6 NC VIN 4 5 VOUT 8-pin MSOP (MM) Pin Description Pin Number Pin Name 1 CBYP Reference Bypass: Connect external 0.01F capacitor to GND to reduce output noise. May be left open. 2 DELAY Delay Set Input: Connect external capacitor to GND to set the delay of the Error Flag. 3 GND Ground. 4 VIN Supply Input. 5 VOUT 6 NC 7 RESET 8 ENABLE M0382-033004 Pin Function Regulator Output. No Connect. RESET Output: Open-drain output. Active low indicates an output undervoltage condition. Enable Input: CMOS compatible input. Logic high = enable; Logic low = shutdown. Do not leave open. 2 March 2004 MIC5249 Micrel Absolute Maximum Ratings(1) Operating Ratings(2) Supply Input Voltage (VIN) .................................. 0V to +7V Power Dissipation (PD) ........................ Internally Limited(3) Junction Temperature .............................. –40°C to +125°C Lead Temperature (soldering, 5 sec.) ....................... 260°C Storage Temperature (TS) ......................... –65°C to 150°C ESD Rating(4) Supply Input Voltage (VIN) ............................. +2.7V to +6V Enable Input Voltage (VEN) .................................. 0V to VIN Junction Temperature (TJ) ....................... –40°C to +125°C Package Thermal Resistance MSOP-8 (θJA ) ................................................... 200°C/W Electrical Characteristics VIN = VOUT +1.0V; COUT = 1.0µF, IOUT = 100µA; TJ = 25°C, bold values indicate –40°C to + 125°C; unless noted. Parameter Conditions Min Output Voltage Accuracy Variation from nominal VOUT –1.0 –3.0 Line Regulation VIN = VOUT +1V to 6V –0.3 Load Regulation IOUT = 0.1mA to 300mA Dropout Voltage IOUT = 100µA 1 IOUT = 150mA 160 225 275 mV mV IOUT = 300mA 340 500 600 mV mV IOUT = 0mA 85 150 µA IOUT = 300mA 100 200 µA Ground Pin Current in Shutdown VEN < 0.4V (Regulator OFF) 0.35 1 µA Ripple Rejection f = 120Hz, COUT = 2.2µF Current Limit VOUT = 0V Ground Pin Current 300 Typ Max Units +1.0 +3.0 % % 0.02 +0.3 %/V 1.5 3.0 % mV 65 dB 440 mA Enable Input Enable Input Voltage Logic low (regulator shutdown) 0.4 Logic high (regulator enabled) Enable Input Current 1.6 V V VIL < 0.4V (regulator shutdown) 0.01 µA VIH > 1.6V (regulator enabled) 0.01 µA Delay Input Delay Pin Current Source Delay Pin Threshold Voltage 0.55 Threshold for RESET = Logic high 1 µA 1.40 V 91 % RESET Output VTH Low threshold, % of VOUT (Flag ON) High threshold, % of VOUT (Flag OFF) 89 93 96 % 0.1 V VOL RESET output logic – low voltage; IRESET = 100µA output in fault condition 0.020 IRESET Flag leakage current, Flag OFF 0.01 µA Notes: 1. Exceeding maximum rating may damage the device. 2. The device is not guaranteed to work outside its operating rating. 3. The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = TJ(max) – TA) ÷ θJA. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 4. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. March 2004 3 M0382-033004 MIC5249 Micrel Functional Diagram EN VREF IN Startup/ Shutdown Control Quickstart/ Noise Cancellation Error Amplifier Thermal Sensor BYP Current Amplifier OUT Undervoltage Lockout Out of Regulation RESET Overcurrent Dropout Detection Delay M0382-033004 4 GND March 2004 MIC5249 Micrel Reset Output The RESET output of the MIC5249 provides the power-on reset signal based on the capacitor from the DELAY pin to ground when input power is applied to the regulator. The reset signal stays low for a preset time period after power is applied to the regulator, and then goes high (see “Timing Diagram”). The reset output is an active-low, open-drain output that drives low when a fault condition AND an undervoltage detection occurs. Internal circuitry intelligently monitors overcurrent, overtemperature and dropout conditions and ORs these outputs together to indicate some fault condition. The output of that OR gate is ANDed with an output voltage monitor that detects an undervoltage condition. The output drives an open-drain transistor to indicate a fault. This prevents chattering or inadvertent triggering of the reset. The reset must be pulled up using a resistor form the RESET pin to either the input or the output. Bypass Pin Input A bypass capacitor is required from the noise bypass pin to ground to reduce output voltage noise. The capacitor bypasses the internal reference. A 0.01µF capacitor is recommended for applications that require low-noise outputs. The bypass capacitor can be increased, further reducing noise and improving PSRR. Turn-on time increases slightly with respect to bypass capacitance. A unique quick-start circuit allows the MIC5249 to drive a large capacitor on the bypass pin without significantly slowing the turn-on time. Active Shutdown The MIC5249 also features an active shutdown clamp, which is a N-Channel MOSFET that turns on when the device is disabled. This allows the output capacitor and load to discharge, de-energizing the load. No-Load Stability The MIC5249 will remain stable and in regulation with no load unlike many other voltage regulators. This is especially important in CMOS RAM keep-alive application. Applications Information Enable/Shutdown The MIC5249 comes with an active-high enable pin that allows the regulator to be disabled. Forcing the enable pin low disables the regulator and sends it into a “zero” off-modecurrent state. In this state, current consumed by the regulator goes nearly to zero. Forcing the enable pin high enables the output voltage. This part is CMOS and the enable pin cannot be left floating; a floating enable pin may cause an indeterminate state on the output. Input Capacitor The MIC5249 is a high performance, high bandwidth device. Therefore, it requires a well-bypassed input supply for optimal performance. A 1.0µF capacitor is required from the input to ground to provide stability. Low-ESR ceramic capacitors provide optimal performance at a minimum of space. Additional high-frequency capacitors such as small valued NPO dielectric type capacitors help to filter out high frequency noise and are good practice in any RF-based circuit. Output Capacitor The MIC5249 requires an output capacitor for stability. The design requires 2.2µF or greater on the output to maintain stability. The design is optimized for use with low-ESR ceramic chip capacitors. High-ESR capacitors may cause high frequency oscillation. The maximum recommended ESR is 300mΩ. The output capacitor can be increased, but performance has been optimized for a 2.2µF ceramic output capacitor and does not improve significantly with larger capacitance. X7R/X5R dielectric-type ceramic capacitors are recommended because of their temperature performance. X7Rtype capacitors change capacitance by 15% over their operating temperature range and are the most stable type of ceramic capacitors. Z5U and Y5V dielectric capacitors change value by as much as 50% and 60%, respectively, over their operating temperature ranges. To use a ceramic chip capacitor with Y5V dielectric, the value must be much higher than an X7R ceramic capacitor to ensure the same minimum capacitance over the equivalent operating temperature range. Delay Pin Input The power-on reset function can be implemented on the MIC5249 by adding an external capacitor from the delay pin to ground. This external capacitor sets the delay time (TDELAY) of the RESET output. The capacitor value required can be easily calculated using the formula: T ×I CDELAY = DELAY DELAY VDELAY where IDELAY is 0.55µA and the VDELAY is 1.4V. When no capacitor is used, there will be no delay and the POR output acts like a standard error FLAG output. March 2004 5 M0382-033004 MIC5249 Micrel Thermal Consideration The MIC5249 is designed to provide 300mA of continuous current in a very small package. Maximum power dissipation can be calculated based on the output current and the voltage drop across the device. To determine the maximum power dissipation of the package, use the junction-to-ambient thermal resistance of the device and the following basic equation: Substituting PD(max) for PD and solving for the operating conditions that are critical to the application will give the maximum operating conditions for the regulator circuit. For example, when operating the MIC5249-3.0BMM at 50°C with a minimum footprint layout, the maximum input voltage for a set output current can be determined as follows: 125°C − 50°C PD (max) = 200°C/W T (max) − TA PD (max) = J θ JA The junction-to-ambient thermal resistance for the minimum footprint is 200°C/W, from Table 1. The maximum power dissipation must not be exceeded for proper operation. Using the output voltage of 3.0V, and an output current of 300mA, the maximum input voltage can be determined. Because this device is CMOS and the ground current is typically 90µA over the load range, the power dissipation contributed by the ground current is < 1.0% and can be ignored for this calculation. 375mW = (VIN – 3.0V)300mA 375mW = VIN × 300mA – 900mW TJ(max) is the maximum junction temperature of the die, 125°C and TA is the ambient operating temperature. θJA i s layout dependent; Table 1 shows examples of the junctionto-ambient thermal resistance for the MIC5249. θJA Recommended Minimum Footprint MSOP-8 (MM) 200°C/W Table 1. MSOP-8 Thermal Resistance Package 1275mW = VIN × 300mA VIN(max) = 4.25V Therefore, a 3.0V application at 300mA of output current can accept a maximum input voltage of 4.25V in the MSOP-8 package. For a full discussion of heat sinking and thermal effects on the voltage regulators, refer to the “Regulator Thermals” section of Micrel’s Designing with Low-Dropout The actual power dissipation of the regulator circuit can be determined using the equation: PD = (VIN – VOUT ) IOUT + VIN IGND Voltage Regulators Handbook. M0382-033004 6 March 2004 MIC5249 Micrel Package Information 0.199 (5.05) 0.187 (4.74) 0.122 (3.10) 0.112 (2.84) DIMENSIONS: INCH (MM) 0.120 (3.05) 0.116 (2.95) 0.036 (0.90) 0.032 (0.81) 0.043 (1.09) 0.038 (0.97) 0.012 (0.30) R 0.008 (0.20) 0.004 (0.10) 0.012 (0.3) 0.0256 (0.65) TYP 5° MAX 0° MIN 0.007 (0.18) 0.005 (0.13) 0.012 (0.03) R 0.039 (0.99) 0.035 (0.89) 0.021 (0.53) 8-Lead MSOP (MM) MICREL, INC. TEL 1849 FORTUNE DRIVE SAN JOSE, CA 95131 + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB USA http://www.micrel.com The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can 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 Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale. © 2004 Micrel, Incorporated. March 2004 7 M0382-033004