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MIC5249
Micrel
MIC5249
300mA Cap LDO with Programmable Power-On Reset Delay
General Description
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.
Features
* * * * * 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: 85A 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 MIC5249-1.8BMM MIC5249-2.5BMM MIC5249-2.6BMM MIC5249-2.8BMM MIC5249-2.85BMM MIC5249-3.0BMM Voltage* 1.8V 2.5V 2.6V 2.8V 2.85V 3.0V Junction Temp. Range -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C Package MSOP-8 MSOP-8 MSOP-8 MSOP-8 MSOP-8 MSOP-8
* Other voltages available. Contact Micrel for details.
Typical Application
MIC5249-x.xBMM VIN
ENABLE SHUTDOWN
IN EN
OUT RESET
VOUT RESET
DELAY CBYP CAD=1.0F Ceramic GND COUT=2.2F Ceramic CBYP=0.01F
Sets the delay for the RESET output
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
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Pin Configuration
CBYP 1 DELAY 2 GND 3 VIN 4 8 ENABLE 7 RESET 6 NC 5 VOUT
8-pin MSOP (MM)
Pin Description
Pin Number 1 2 3 4 5 6 7 8 Pin Name CBYP DELAY GND VIN VOUT NC RESET ENABLE Pin Function Reference Bypass: Connect external 0.01F capacitor to GND to reduce output noise. May be left open. Delay Set Input: Connect external capacitor to GND to set the delay of the Error Flag. Ground. Supply Input. 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.
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Absolute Maximum Ratings(1)
Supply Input Voltage (VIN) .................................. 0V to +7V Power Dissipation (PD) ........................ Internally Limited(3) Junction Temperature .............................. -40C to +125C Lead Temperature (soldering, 5 sec.) ....................... 260C Storage Temperature (TS) ......................... -65C to 150C ESD Rating(4)
Operating Ratings(2)
Supply Input Voltage (VIN) ............................. +2.7V to +6V Enable Input Voltage (VEN) .................................. 0V to VIN Junction Temperature (TJ) ....................... -40C to +125C Package Thermal Resistance MSOP-8 (JA ) ................................................... 200C/W
Electrical Characteristics
VIN = VOUT +1.0V; COUT = 1.0F, IOUT = 100A; TJ = 25C, bold values indicate -40C to + 125C; unless noted. Parameter Output Voltage Accuracy Line Regulation Load Regulation Dropout Voltage Conditions Variation from nominal VOUT VIN = VOUT +1V to 6V IOUT = 0.1mA to 300mA IOUT = 100A IOUT = 150mA IOUT = 300mA Ground Pin Current IOUT = 0mA IOUT = 300mA Ground Pin Current in Shutdown Ripple Rejection Current Limit Enable Input Enable Input Voltage Logic low (regulator shutdown) Logic high (regulator enabled) Enable Input Current VIL < 0.4V (regulator shutdown) VIH > 1.6V (regulator enabled) Delay Input Delay Pin Current Source Delay Pin Threshold Voltage RESET Output VTH VOL IRESET
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) / JA. 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.
Min -1.0 -3.0 -0.3
Typ
Max +1.0 +3.0
Units % % %/V % mV
0.02 1.5 1 160 340 85 100 0.35 65
+0.3 3.0
225 275 500 600 150 200 1
mV mV mV mV A A A dB mA
VEN < 0.4V (Regulator OFF) f = 120Hz, COUT = 2.2F VOUT = 0V 300
440
0.4 1.6 0.01 0.01
V V A A A V
0.55 Threshold for RESET = Logic high 1.40
1
Low threshold, % of VOUT (Flag ON) High threshold, % of VOUT (Flag OFF) RESET output logic - low voltage; IRESET = 100A output in fault condition Flag leakage current, Flag OFF
89
91 93 0.020 0.01 96 0.1
% % V A
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Functional Diagram
EN
IN
VREF
Startup/ Shutdown Control
Quickstart/ Noise Cancellation
BYP
Thermal Sensor
Error Amplifier
Current Amplifier
OUT
Undervoltage Lockout Out of Regulation RESET Overcurrent Dropout Detection
Delay
GND
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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 0.01F 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 1.0F 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 2.2F 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 300m. The output capacitor can be increased, but performance has been optimized for a 2.2F 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 xI CDELAY = DELAY DELAY VDELAY
where IDELAY is 0.55A 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.
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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:
T (max) - TA PD (max) = J JA
Micrel
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 50C with a minimum footprint layout, the maximum input voltage for a set output current can be determined as follows:
125C - 50C PD (max) = 200C/W
TJ(max) is the maximum junction temperature of the die, 125C and TA is the ambient operating temperature. JA i s layout dependent; Table 1 shows examples of the junctionto-ambient thermal resistance for the MIC5249. JA Recommended Minimum Footprint MSOP-8 (MM) 200C/W Table 1. MSOP-8 Thermal Resistance Package The actual power dissipation of the regulator circuit can be determined using the equation: PD = (VIN - VOUT ) IOUT + VIN IGND
The junction-to-ambient thermal resistance for the minimum footprint is 200C/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 90A 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 x 300mA - 900mW 1275mW = VIN x 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
Voltage Regulators Handbook.
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Package Information
0.122 (3.10) 0.112 (2.84)
0.199 (5.05) 0.187 (4.74)
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
0.007 (0.18) 0.005 (0.13)
0.012 (0.3) 0.0256 (0.65) TYP
0.008 (0.20) 0.004 (0.10)
5 MAX 0 MIN
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
FAX
USA
+ 1 (408) 944-0800
+ 1 (408) 944-0970
WEB
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. (c) 2004 Micrel, Incorporated.
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