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MIC5209
500mA Low-Noise LDO Regulator
General Description
The MIC5209 is an efficient linear voltage regulator with very low dropout voltage, typically 10mV at light loads and less than 500mV at full load, with better than 1% output voltage accuracy. Designed especially for hand-held, battery-powered devices, the MIC5209 features low ground current to help prolong battery life. An enable/shutdown pin on SO-8 and TO-2635 versions can further improve battery life with near-zero shutdown current. Key features include reversed-battery protection, current limiting, overtemperature shutdown, ultra-low-noise capability (SO-8 and TO-263-5 versions), and availability in thermally efficient packaging. The MIC5209 is available in adjustable or fixed output voltages. For space-critical applications where peak currents do not exceed 500mA, see the MIC5219.
Features
* Meets Intel(R) Slot 1 and Slot 2 requirements * Guaranteed 500mA output over the full operating temperature range * Low 500mV maximum dropout voltage at full load * Extremely tight load and line regulation * Thermally-efficient surface-mount package * Low temperature coefficient * Current and thermal limiting * Reversed-battery protection * No-load stability * 1% output accuracy * Ultra-low-noise capability in SO-8 and TO-263-5 * Ultra-small 3mm x 3mm MLFTM package
Applications
* * * * * * Pentium II Slot 1 and Slot 2 support circuits Laptop, notebook, and palmtop computers Cellular telephones Consumer and personal electronics SMPS post-regulator/dc-to-dc modules High-efficiency linear power supplies
Typical Applications
MIC5209-2.5BS
VIN 3.0V
1
2
3
VOUT 2.5V 1% 22F tantalum
0.1F
3.3V Nominal-Input Slot-1 Power Supply
ENABLE SHUTDOWN
1 2 3 4
MIC5209-5.0BM
8 7 6 5
VIN 6V VOUT 5V
2.2F tantalum
470pF
(OPTIONAL)
Ultra-Low-Noise 5V Regulator
Micrel, Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
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MIC5209
Micrel, Inc. Voltage 2.5V 2.5V 3.0V 3.0V 3.3V 3.3V 3.6V 3.6V 4.2V 4.2V 5.0V 5.0V 1.8V 1.8V 2.5V 2.5V 3.0V 3.0V 3.3V 3.3V 3.6V 3.6V 5.0V 5.0V Adj. Adj. 1.8V 2.5V 2.5V 3.0V 3.0V 3.3V 3.3V 3.6V 3.6V 5.0V 5.0V Adj. Adj. Adj. Junction Temp. Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -0C to +125C -0C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -0C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C Package SOT-223 SOT-223 SOT-223 SOT-223 SOT-223 SOT-223 SOT-223 SOT-223 SOT-223 SOT-223 SOT-223 SOT-223 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 SOIC-8 TO-263-5 TO-263-5 TO-263-5 TO-263-5 TO-263-5 TO-263-5 TO-263-5 TO-263-5 TO-263-5 TO-263-5 TO-263-5 TO-263-5 TO-263-5 8-pin MLFTM X X X X X X X X X X X X X X X X X X X X X Pb-Free
Ordering Information
Part Number MIC5209-2.5BS MIC5209-2.5YS MIC5209-3.0BS MIC5209-3.0YS MIC5209-3.3BS MIC5209-3.3YS MIC5209-3.6BS MIC5209-3.6YS MIC5209-4.2BS MIC5209-4.2YS MIC5209-5.0BS MIC5209-5.0YS MIC5209-1.8BM* MIC5209-1.8YM* MIC5209-2.5BM MIC5209-2.5YM MIC5209-3.0BM MIC5209-3.0YM MIC5209-3.3BM MIC5209-3.3YM MIC5209-3.6BM MIC5209-3.6YM MIC5209-5.0BM MIC5209-5.0YM MIC5209BM MIC5209YM MIC5209-1.8YU* MIC5209-2.5BU MIC5209-2.5YU MIC5209-3.0BU MIC5209-3.0YU MIC5209-3.3BU MIC5209-3.3YU MIC5209-3.6BU MIC5209-3.6YU MIC5209-5.0BU MIC5209-5.0YU MIC5209BU MIC5209YU MIC5209YML
* Contact marketing for availability.
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MIC5209
Micrel, Inc.
GND
TAB
Pin Configuration
VIN 1 VIN 2 VOUT 3 Y 5209 YWW
8 7 6 5
EN GND ADJ NC
Part Identification
1
2
3
VOUT 4
IN
GND OUT
MIC5209-x.xBS SOT-223 Fixed Voltages
EN 1 IN 2 OUT 3 BYP 4 8 7 6 5 GND
GND
TAB
MIC5209YML 8-Pin 3x3 MLF Adjustable Voltages
5 4 3 2 1 BYP OUT GND IN EN
GND GND GND
MIC5209-x.xBM SO-8 Fixed Voltages
MIC5209-x.xBU TO-263-5 Fixed Voltages
EN 1 IN 2 OUT 3 ADJ 4
8 7 6 5
GND GND GND GND
5 4 3 2 1
ADJ OUT GND IN EN
GND Pin Name IN GND OUT EN BYP Pin Function Supply Input. ADJ
TAB A
MIC5209BM SO-8 Adjustable Voltage
MIC5209BU TO-263-5 Adjustable Voltage
Pin Description
Pin No. 8-pin MLF 1, 2 7 3, 4 8 Pin No. SOT-223 1 2, TAB 3 Pin No. SO-8 2 5-8 3 1 4 (fixed) Pin No. TO-263-5 2 3 4 1 5 (fixed)
Ground: SOT-223 pin 2 and TAB are internally connected. SO-8 pins 5 through 8 are internally connected. Regulator Output. Pins 3 and 4 must be tied together. Enable (Input): CMOS compatible control input. Logic high = enable; logic low = shutdown. Reference Bypass: Connect external 470pF capacitor to GND to reduce output noise. May be left open. For 1.8V or 2.5V operation, see "Applications Information." Adjust (Input): Feedback input. Connect to resistive voltage-divider network.
6
4 (adj.)
5 (adj.)
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Absolute Maximum Ratings(1)
Supply Input Voltage (VIN) ..............................-20V to +20V Power Dissipation (PD) ..........................Internally Limited(3) Junction Temperature (TJ) all except 1.8V ...................................... -40C to +125C 1.8V only................................................... 0C to +125C Lead Temperature (soldering, 5 sec.) ........................ 260C Storage Temperature (TS) ........................ -65C to +150C
Operating Ratings(2)
Supply Input Voltage (VIN) ............................ +2.5V to +16V Enable Input Voltage (VEN) ...................................0V to VIN Junction Temperature (TJ) all except 1.8V ...................................... -40C to +125C 1.8V only................................................... 0C to +125C Package Thermal Resistance................................... Note 3
Electrical Characteristics (Note 11)
VIN = VOUT + 1.0V; COUT = 4.7F, IOUT = 100A; TJ = 25C, bold values indicate -40C TJ +125C except 0C TJ +125C for 1.8V version; unless noted. Symbol VOUT VOUT/T VOUT/VOUT VOUT/VOUT VIN - VOUT Parameter Output Voltage Accuracy Output Voltage Temperature Coefficient Line Regulation Load Regulation Dropout Voltage(6) Conditions variation from nominal VOUT Note 4 VIN = VOUT + 1V to 16V IOUT = 100A to 500mA(5) IOUT = 100A IOUT = 50mA IOUT = 150mA IOUT = 500mA IGND Ground Pin Current(7, 8) VEN 3.0V, IOUT = 100A VEN 3.0V, IOUT = 50mA VEN 3.0V, IOUT = 150mA VEN 3.0V, IOUT = 500mA IGND PSRR ILIMIT VOUT/PD eno Ground Pin Quiescent Current(8) Ripple Rejection Current Limit Thermal Regulation Output Noise(10) VEN 0.4V (shutdown) f = 120Hz Min -1 -2 40 0.009 0.05 10 115 165 350 80 350 1.8 8 0.05 0.10 75 700 0.05 500 300 900 1000 0.05 0.1 0.5 0.7 60 80 175 250 300 400 500 600 130 170 650 900 2.5 3.0 20 25 3 8 Typical Max 1 2 Units % % ppm/C %/V %/V % % mV mV mV mV mV mV mV mV A A A A mA mA mA mA A A dB mA mA %/W nV Hz nV Hz
VEN 0.18V (shutdown)
VOUT = 0V Note 9 VOUT = 2.5V, IOUT = 50mA, COUT = 2.2F, CBYP = 0
IOUT = 50mA, COUT = 2.2F, CBYP = 470pF
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ENABLE Input VENL Enable Input Logic-Low Voltage VEN = logic low (regulator shutdown) VEN = logic high (regulator enabled) VENL 0.18V VENH = 2.0V 2.0 0.01 0.01 5
Micrel, Inc.
0.4 0.18 -1 -2 20 25 30 50 V V V A A A A A A
IENL IENH
Enable Input Current
VENL 0.4V
VENH = 16V
Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating.
3. The maximum allowable power dissipation at any TA (ambient temperature) is calculated using: 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. See Table 1 and the "Thermal Considerations" section for details. 4. Output voltage temperature coefficient is the worst case voltage change divided by the total temperature range. 5. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load range from 100A to 500mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification. 6. Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1V differential. 7. Ground pin current is the regulator quiescent current plus pass transistor base current. The total current drawn from the supply is the sum of the load current plus the ground pin current. 8. VEN is the voltage externally applied to devices with the EN (enable) input pin. [SO-8 (M) and TO-263-5 (U) packages only.] 9. Thermal regulation is the change in output voltage at a time "t" after a change in power dissipation is applied, excluding load or line regulation effects. Specifications are for a 500mA load pulse at VIN = 16V for t = 10ms.
10. CBYP is an optional, external bypass capacitor connected to devices with a BYP (bypass) or ADJ (adjust) pin. [SO-8 (M) and TO-263-5 (U) packages only].
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Block Diagrams
VIN IN OUT VOUT COUT
Bandgap Ref. Current Limit Thermal Shutdown MIC5209-x.xBS GND
Low-Noise Fixed Regulator (SOT-223 version only)
IN BYP CBYP (optional) Bandgap Ref. VREF EN Current Limit Thermal Shutdown MIC5209-x.xBM/U GND OUT VOUT COUT
VIN
Ultra-Low-Noise Fixed Regulator
IN OUT VOUT COUT ADJ Bandgap Ref. VREF EN Current Limit Thermal Shutdown MIC5209BM/U [adj.] GND R1 R2 CBYP (optional)
VIN
Ultra-Low-Noise Adjustable Regulator
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Typical Characteristics
Power Supply Rejection Ratio
VIN = 6V VOUT = 5V
PSRR (dB)
0 -20 PSRR (dB) -40 -60 -80
0 -20 -40 -60 -80
Power Supply Rejection Ratio
VIN = 6V VOUT = 5V
PSRR (dB)
0 -20 -40 -60 -80
Power Supply Rejection Ratio
VIN = 6V VOUT = 5V
-100 1E+1 1E+21E+3 1E+41E+5 1E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
IOUT = 100A COUT = 1F
-100 1E+1 1E+21E+3 1E+41E+5 1E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
IOUT = 1mA COUT = 1F
IOUT = 100mA COUT = 1F
-100 1E+1 1E+21E+3 1E+41E+5 1E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
0 -20 PSRR (dB) -40 -60 -80
Power Supply Rejection Ratio
VIN = 6V VOUT = 5V
PSRR (dB)
0 -20 -40 -60 -80
Power Supply Rejection Ratio
VIN = 6V VOUT = 5V
PSRR (dB)
0 -20 -40 -60 -80
Power Supply Rejection Ratio
VIN = 6V VOUT = 5V
-100 1E+1 1E+21E+3 1E+41E+5 1E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
IOUT = 100A COUT = 2.2F CBYP = 0.01F
-100 1E+1 1E+21E+3 1E+41E+5 1E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
IOUT = 1mA COUT = 2.2F CBYP = 0.01F
-100 1E+1 1E+21E+3 1E+41E+5 1E+61E+7 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz)
IOUT = 100mA COUT = 2.2F CBYP = 0.01F
Power Supply Ripple Rejection vs. Voltage Drop
60 50 40 30 20 10 0 0 COUT = 1F 0.1 0.2 0.3 VOLTAGE DROP (V) 0.4 1mA 10mA IOUT = 100mA
100 90 80 70 60 50 40 30 20 10 0 0
Power Supply Ripple Rejection vs. Voltage Drop
1mA
10 1 NOISE (V/Hz) 0.1 0.01 0.001
Noise Performance
10mA, C OUT = 1F
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
10mA
IOUT = 100mA
COUT = 2.2F CBYP = 0.01F 0.1 0.2 0.3 VOLTAGE DROP (V) 0.4
VOUT = 5V 0.0001 10 100 1k 10k 100k 1M 10M 1E+11E+2 1E+31E+4 1E+51E+6 1E+7 FREQUENCY (Hz)
10 1
Noise Performance
100mA 10mA
10 1 NOISE (V/Hz) 0.1
Noise Performance
400 DROPOUT VOLTAGE (mV) 300 200 100 0 0
Dropout Voltage vs. Output Current
NOISE (V/Hz)
100mA
0.1 0.01
VOUT = 5V 1mA 0.001 C OUT = 10F electrolytic 0.0001 10 100 1k 10k 100k 1M 10M 1E+1 1E+2 1E+31E+4 1E+51E+6 1E+7 FREQUENCY (Hz)
0.01 V OUT = 5V COUT = 10F 0.001 electrolytic CBYP = 100pF
1mA 10mA
0.0001 10 100 1k 10k 100k 1M 10M 1E+1 1E+21E+3 1E+41E+5 1E+61E+7 FREQUENCY (Hz)
100 200 300 400 500 OUTPUT CURRENT (mA)
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Dropout Characteristics
3.5 OUTPUT VOLTAGE (V) 3.0 2.5 2.0 1.5 1.0 0.5 0 0 1 IL=100mA IL=500mA 2345678 INPUT VOLTAGE (V) 9 GROUND CURRENT (mA) IL =100A 12 10 8 6 4 2 0 0
Ground Current vs. Output Current
100 200 300 400 500 OUTPUT CURRENT (mA)
25
Ground Current vs. Supply Voltage
3.0
Ground Current vs. Supply Voltage
GROUND CURRENT (mA)
20 15 10 5 0 0 IL=500mA 12345678 INPUT VOLTAGE (V) 9
GROUND CURRENT (mA)
2.5 2.0 1.5 1.0 0.5 0 0 IL=100 mA IL=100 A8 4 6 2 INPUT VOLTAGE (V)
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Micrel, Inc. Thermal Considerations The SOT-223 has a ground tab which allows it to dissipate more power than the SO-8. Refer to "Slot-1 Power Supply" for details. At 25C ambient, it will operate reliably at 2W dissipation with "worst-case" mounting (no ground plane, minimum trace widths, and FR4 printed circuit board). Thermal resistance values for the SO-8 represent typical mounting on a 1"-square, copper-clad, FR4 circuit board. For greater power dissipation, SO-8 versions of the MIC5209 feature a fused internal lead frame and die bonding arrangement that reduces thermal resistance when compared to standard SO-8 packages.
Package SOT-223 (S) SO-8 (M) TO-263-5 (U) 3x3 MLF (ML) 50C/W 50C/W -- 63C/W JA 8C/W 20C/W 2C/W 2C/W JC
Applications Information
Enable/Shutdown Enable is available only on devices in the SO-8 (M) and TO-263-5 (U) packages. Forcing EN (enable/shutdown) high (> 2V) enables the regulator. EN is compatible with CMOS logic. If the enable/shutdown feature is not required, connect EN to IN (supply input). Input Capacitor A 1F capacitor should be placed from IN to GND if there is more than 10 inches of wire between the input and the ac filter capacitor or if a battery is used as the input. Output Capacitor An output capacitor is required between OUT and GND to prevent oscillation. The minimum size of the output capacitor is dependent upon whether a reference bypass capacitor is used. 1F minimum is recommended when CBYP is not used (see Figure 1). 2.2F minimum is recommended when CBYP is 470pF (see Figure 2). Larger values improve the regulator's transient response. The output capacitor should have an ESR (equivalent series resistance) of about 1 and a resonant frequency above 1MHz. Ultra-low-ESR capacitors can cause a low amplitude oscillation on the output and/or underdamped transient response. Most tantalum or aluminum electrolytic capacitors are adequate; film types will work, but are more expensive. Since many aluminum electrolytics have electrolytes that freeze at about -30C, solid tantalums are recommended for operation below -25C. At lower values of output current, less output capacitance is needed for output stability. The capacitor can be reduced to 0.47F for current below 10mA or 0.33F for currents below 1mA. No-Load Stability The MIC5209 will remain stable and in regulation with no load (other than the internal voltage divider) unlike many other voltage regulators. This is especially important in CMOS RAM keep-alive applications. Reference Bypass Capacitor BYP (reference bypass) is available only on devices in SO-8 and TO-263-5 packages. BYP is connected to the internal voltage reference. A 470pF capacitor (CBYP) connected from BYP to GND quiets this reference, providing a significant reduction in output noise (ultra-low-noise performance). Because CBYP reduces the phase margin, the output capacitor should be increased to at least 2.2F to maintain stability. The start-up speed of the MIC5209 is inversely proportional to the size of the reference bypass capacitor. Applications requiring a slow ramp-up of output voltage should consider larger values of CBYP. Likewise, if rapid turn-on is necessary, consider omitting CBYP.
Table 1. MIC5209 Thermal Resistance Multilayer boards with a ground plane, wide traces near the pads, and large supply-bus lines will have better thermal conductivity and will also allow additional power dissipation. For additional heat sink characteristics, please refer to Micrel Application Hint 17, "Designing P.C. Board Heat Sinks", included in Micrel's Databook. For a full discussion of heat sinking and thermal effects on voltage regulators, refer to Regulator Thermals section of Micrel's Designing with LowDropout Voltage Regulators handbook. Low-Voltage Operation The MIC5209-1.8 and MIC5209-2.5 require special consideration when used in voltage-sensitive systems. They may momentarily overshoot their nominal output voltages unless appropriate output and bypass capacitor values are chosen. During regulator power up, the pass transistor is fully saturated for a short time, while the error amplifier and voltage reference are being powered up more slowly from the output (see "Block Diagram"). Selecting larger output and bypass capacitors allows additional time for the error amplifier and reference to turn on and prevent overshoot. To ensure that no overshoot is present when starting up into a light load (100A), use a 4.7F output capacitance and 470pF bypass capacitance. This slows the turn-on enough to allow the regulator to react and keep the output voltage from exceeding its nominal value. At heavier loads, use a 10F output capacitance and 470pF bypass capacitance. Lower values of output and bypass capacitance can be used, depending on the sensitivity of the system. Applications that can withstand some overshoot on the output of the regulator can reduce the output capacitor and/or reduce or eliminate the bypass capacitor. Applications that are not sensitive to overshoot due to power-on reset delays can use normal output and bypass capacitor configurations. Please note the junction temperature range of the regulator at 1.8V output (fixed and adjustable) is 0C to +125C. 9
If output noise is not critical, omit CBYP and leave BYP open.
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MIC5209 Fixed Regulator Circuits MIC5209-x.xBM VIN 2 3 IN OUT 1 4 EN BYP GND
5-8
Micrel, Inc.
VOUT
VIN MIC5209BM
2 1
IN EN
OUT ADJ GND
5-8
3 4
VOUT R1 R2 2.2F
1F
470pF
Figure 1. Low-Noise Fixed Voltage Regulator Figure 1 shows a basic MIC5209-x.xBM (SO-8) fixed-voltage regulator circuit. See Figure 5 for a similar configuration using the more thermally-efficient MIC5209-x.xBS (SOT-223). A 1F minimum output capacitor is required for basic fixedvoltage applications.
VIN MIC5209-x.xBM
2 1
Figure 4. Ultra-Low-Noise Adjustable Application. Figure 4 includes the optional 470pF bypass capacitor from ADJ to GND to reduce output noise. Slot-1 Power Supply Intel's Pentium II processors have a requirement for a 2.5V 5% power supply for a clock synthesizer and its associated loads. The current requirement for the 2.5V supply is dependant upon the clock synthesizer used, the number of clock outputs, and the type of level shifter (from core logic levels to 2.5V levels). Intel estimates a worst-case load of 320mA. The MIC5209 was designed to provide the 2.5V power requirement for Slot-1 applications. Its guaranteed performance of 2.5V 3% at 500mA allows adequate margin for all systems, and its dropout voltage of 500mV means that it operates from a worst-case 3.3V supply where the voltage can be as low as 3.0V.
VIN CIN 0.1F MIC5209-x.xBS
1
IN EN
OUT BYP GND
5-8
3 4
VOUT 2.2F
470pF
Figure 2. Ultra-Low-Noise Fixed Voltage Regulator Figure 2 includes the optional 470pF noise bypass capacitor between BYP and GND to reduce output noise. Note that the minimum value of COUT must be increased when the bypass capacitor is used. Adjustable Regulator Circuits
VIN MIC5209BM
2 1
IN
OUT GND
2,TAB
3
VOUT COUT 22F
IN EN
OUT ADJ GND
5-8
3 4
VOUT R1 R2 1F
Figure 5. Slot-1 Power Supply A Slot-1 power supply (Figure 5) is easy to implement. Only two capacitors are necessary, and their values are not critical. CIN bypasses the internal circuitry and should be at least 0.1F. COUT provides output filtering, improves transient response, and compensates the internal regulator control loop. Its value should be at least 22F. CIN and COUT may be increased as much as desired. Slot-1 Power Supply Power Dissipation Powered from a 3.3V supply, the Slot-1 power supply of Figure 5 has a nominal efficiency of 75%. At the maximum anticipated Slot 1 load (320mA), the nominal power dissipation is only 256mW. The SOT-223 package has sufficient thermal characteristics for wide design margins when mounted on a single layer copper-clad printed circuit board. The power dissipation of the MIC5209 is calculated using the voltage drop across the device x output current plus supply voltage x ground current.
Figure 3. Low-Noise Adjustable Voltage Regulator The MIC5209BM/U can be adjusted to a specific output voltage by using two external resistors (Figure 3). The resistors set the output voltage based on the equation: R2 VOUT = 1.242V 1 + R1 This equation is correct due to the configuration of the bandgap reference. The bandgap voltage is relative to the output, as seen in the block diagram. Traditional regulators normally have the reference voltage relative to ground; therefore, their equations are different from the equation for the MIC5209BM/U. Although ADJ is a high-impedance input, for best performance, R2 should not exceed 470k.
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MIC5209 Considering worst case tolerances, the power dissipation could be as high as: (VIN(max) - VOUT(max)) x IOUT + VIN(max) x IGND [(3.6V - 2.375V) x 320mA] + (3.6V x 4mA) PD = 407mW
Micrel, Inc. Figure 6 shows the necessary copper pad area to obtain specific heat sink thermal resistance (SA) values. The SA values in Table 2 require much less than 500mm2 of copper, according to Figure 6, and can easily be accomplished with the minimum footprint.
70 60 50 40 30 20
Using the maximum junction temperature of 125C and a JC of 8C/W for the SOT-223, 25C/W for the SO-8, or 2C/W for the TO-263 package, the following worst-case heat-sink thermal resistance (SA) requirements are: TJ(max) - TA J(max JA = PD SA = JA = JC
TA 40C 209C/W 201C/W 184C/W 207C/W 50C 184C/W 176C/W 159C/W 182C/W 60C 160C/W 152C/W 135C/W 158C/W 75C 123C/W 115C/W 98C/W 121C/W
10 0 0 2000 4000 6000
JA (limit)
SA SOT-223 SA SO-8 SA TO-263-5
COPPER HEAT SINK AREA (mm2)
Figure 6. PCB Heat Sink Thermal Resistance
Table 2. Maximum Allowable Thermal Resistance Table 2 and Figure 6 show that the Slot-1 power supply application can be implemented with a minimum footprint layout.
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Micrel, Inc.
Package Information
SOT-223 (S)
8-Pin SOIC (M)
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4
Micrel, Inc.
1
2 1 3 1 2 3 4
1
TO-263-5 (U)
8-Pin 3mm x 3mm MLF (ML)
MICREL INC.
TEL
+ 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
This 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 a 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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