Application Hint 7 Micrel Application Hint 7 Using Low Current LDO Regulators by Bob Wolbert General Description Features The MIC2951 brings the benefits of linear regulation to surface mountable packaging. High accuracy, high efficiency, very low ripple, and excellent protective features are combined into a useful device for laptop/notebook computers, communications equipment, and battery operated instrumentation. +7V * * * * * * High accuracy +5V or adjustable output voltage Extremely small size; up to 150mA output current Low dropout voltage and quiescent curent Thermal and over-current protection Error flag warns of output dropout Logic-controlled electronic shutdown MIC Versus LP Benefits 8 +VIN SHUTDOWN INPUT 3 VCC OUT VOUT 1 SD MIC2951 0V + ON 300k 1% 100pF FB 7 GND 4 220k 1% 180k 1% Part Number LP2951-02BM LP2951-03BM MIC2951-02BM MIC2951-03BM 2N2222 3.3V MIC2951 Configured as a selectable 3.3V or 5.0V output regulator. Pin Configuration 8 SENSE 2 7 SHUTDOWN 3 6 4 5 OUTPUT FEEDBACK PC Board Dielectric FR4 Ceramic ERROR 8-Pin SOIC 8-Pin SOIC 8-Pin SOIC 8-Pin SOIC 1.27 (0.50) BSC 1.75 (0.069) 1.35 (0.053) 0.78 (0.031) 0.61 (0.024) 5.0 (0.197) 4.8 (0.188) 0.37 (0.015) BSC 0.5% 1.0% 0.5% 1.0% 7 (4 PLCS) 3-6 0.22 (0.009) 7 (4 PLCS) 0.19 (0.007) 0.20 (0.008) 0.10 (0.004) Dimensions in mm 160C/W 120C/W 50 mil 245 mil 150 mil 30 mil 50 mil Minimum recommended board pad size Part II. Nominal Power Dissipation and Die Temperature The MIC2951-02/-03BM at a 25C ambient temperature will operate reliably at up to 625mW power dissipation when mounted in the "worst case" manner described above. At an ambient temperature of 55C, the device may safely dissipate 440mW. These power levels are equivalent to a die temperature of 125C, the recommended maximum temperature for non-military grade silicon integrated circuits. 0.77 (0.030) 0.64 (0.025) 45 JA Multi-layer boards having a ground plane, wide traces near the pads, and large supply bus lines provide better thermal conductivity. The "worst case" value of 160C/W assumes no ground plane, minimum trace widths, and a FR4 material board. Pin 1 1997 -40C to + 85C -40C to + 85C -40C to + 85C -40C to + 85C Accuracy 5V TAP 4.0 (0.158) 5.2 (0.205) 6.2 (0.244) 3.8 (0.150) 4.6 (0.181) 5.8 (0.228) 0.45 (0.018) 0.35 (0.014) Temperature Range Package Part I. Layout The MIC2951-02/03BM (8-pin surface mount package) has the following thermal characteristics when mounted on a single layer copper-clad printed circuit board. INPUT Package Dimensions 0.56 (0.022) 0.49 (0.019) 3 Thermal Considerations 1 GROUND Lower dropout voltage 150mA output current vs. 100mA One-sixth the ground current Reverse battery protection for load Survives automotive "Load Dump" transient (60V) Ordering Information 470 k 5V 3.3F * * * * * (inch) 3-187 Application Hint 7 Micrel Typical Applications +5V (+3.15V to +8.9V) MIC2951-02/-03BM common voltage applications. Calculations assume 100mA of output current, 25C ambient temperature, 100% duty cycle, and 160C/W mounting. The Shutdown Input may be left floating if it is not used. + 3.3F 8 +VIN SHUTDOWN INPUT 3 VOUT (+2.85V) VOUT 1 SD MIC2951 0V + ON 100pF GND 4 FB 7 3.3F 130k 1% 100k 1% MIC2951 +2.85V Regulator +5V (+3.3V to +9.0V) +5V (+3.6V to +9.3V) + SHUTDOWN INPUT 3 + 3.3F 8 8 +VIN +VIN VOUT (+3.0V) VOUT 1 SD SHUTDOWN INPUT MIC2951 0V 100pF GND 4 FB 7 3.3F 143k 1% VOUT (+3.3V) VOUT 1 SD MIC2951 0V + ON 3 3.3F + ON 100pF GND 4 FB 7 100k 1% 180k 1% MIC2951 +3.0V Regulator MIC2951 +3.3V Regulator +15V (+12.3V to +17.8V) +18V (+15.3V to +21V) + + 3.3F +VIN 3 +VIN VOUT (+5V) VOUT 1 SD SHUTDOWN INPUT MIC2951 0V SENSE ON GND 4 3.3F 8 8 SHUTDOWN INPUT 5V TAP 6 2 3 VOUT (+12V) VOUT 1 SD MIC2951 0V + 3.3F + ON 100pF GND 4 FB 7 FB 7 MIC2951 +5.0V Regulator MIC2951 +12.0V Regulator +30V (+28.3V to +30V) +18V (+15.3V to +21V) + + 3.3F +VIN +VIN VOUT (+15V) VOUT 1 SD SHUTDOWN INPUT 3 MIC2951 0V 100pF GND 4 FB 7 1.13M 1% VOUT (+28V) VOUT 1 SD MIC2951 0V + ON 3.3F 8 8 3 3.3F 887k 1% 102k 1% (Note: no external resistors are necessary) SHUTDOWN INPUT 3.3F 300k 1% 3.3F + ON 100pF GND 4 FB 7 2.21M 1% 3.3F 102k 1% 102k 1% MIC2951 +15.0V MIC2951 +28.0V Regulator 3-188 1997