SS6642-27GUTB

SS6642G SSC | Alldatasheet

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www.SiliconStandard.com 1 of 22 SS6642G 1/15/2005 Rev.2.10 3-Pin Simple Step-Up DC/DC Converter FEATURES DESCRIPTION A guaranteed start-up from less than 0.9 V. High efficiency. Low quiescent current. Fewer external components needed. Low ripple and low noise. Fixed output voltage: 2.7V, 3.0V, 3.3V, 3.7V, 4.5V and 5V. Space-saving packages: SOT-23, SOT-89 and TO-92.

APPLICATIONS

Pagers. Cameras. Wireless Microphones. Pocket Organizers. Battery Backup Suppliers. Portable Instruments. The SS6642G is a high efficiency step-up DC/DC converter for applications using 1 to 4 NiMH bat- tery cells. Only three external components are re- quired to deliver a fixed output voltage of 2.7V, up from less than 0.9V input with 1mA load. A Pulse Frequency Modulation scheme optimizes performance for applications with light output loading and low input voltages. The output ripple and noise are lower when compared with circuits operating in PSM mode. The PFM control circuit operating at a 100KHz (max.) switching rate results in smaller passive components. The space saving SOT-23, SOT- 89 and TO-92 packages make the SS6642G an ideal choice for DC/DC converter for space con- scious applications, such as pagers, electronic cameras, and wireless microphones. TYPICAL APPLICATION CIRCUIT SS12 VOUTSW GND SS6642-xxG 47µF VOUT 100µH VIN + C1 22µF One Cell Step-Up DC/DC Converter Pb-free, RoHS compliant.

www.SiliconStandard.com 2 of 22 SS6642G 1/15/2005 Rev.2.10 ORDERING INFORMATION PIN CONFIGURATION TO-92 TOP VIEW 1: GND 2: VOUT 3: SW 1 2 3 SOT-89 TOP VIEW 1: GND 2: VOUT 3: SW Packing type T R: Tape and reel T B: Tube Package type GU: RoHS-compliant SOT-23 GX: RoHS-compliant SOT-89 GZ: RoHS-compliant TO-92 Output voltage 27: 2.7V 30: 3.0V 33: 3.3V 37: 3.7V 45: 4.5V 50: 5.0V SS6642-XX XXXX Example: SS6642-27GXTR Æ 2 .7V output version, in RoHS-compliant SOT-89 shipped on tape and reel. SOT-23 TOP VIEW 1: GND 2: SW 3: VOUT Part No. GX SS6642-27G AM27P SS6642-30G AM30P SS6642-33G AM33P SS6642-37G AM37P SS6642-45G AM45P SS6642-50G AM50P SOT-23 MARKING Part No. GU SS6642-27G GM27P SS6642-30G GM30P SS6642-33G GM33P SS6642-37G GM37P SS6642-45G GM45P SS6642-50G GM50P SOT-89 MARKING

www.SiliconStandard.com 3 of 22 SS6642G 1/15/2005 Rev.2.10 ABSOLUTE MAXIMUM RATINGS Supply Voltage (VOUT pin) .6V SW pin Voltage 6V SW pin Switch Current 0.6A Operating Temperature Range -40°C to 85°C Maximum Junction Temperature 125°C Storage Temperature Range -65°C to 150°C Lead Temperature (Soldering 10 Sec.) 260°C Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. TEST CIRCUIT SS12 VOUT SW GND SS6642-xxG 22µF VOUT 100µH VIN + C1 47µF IIN VS VSW SS6642 VOUT SW GND IS Fig. 1 Test Circuit 1 Fig. 2 Test Circuit 2 FOSC SS6642 VS VOUT SW GND 100W Fig. 3 Test Circuit 3

www.SiliconStandard.com 4 of 22 SS6642G 1/15/2005 Rev.2.10 ELECTRICAL CHARACTERISTICS (TA=25°C, IOUT=10mA, unless otherwise specified) (Note1) PARAMETER TEST CONDITIONS TEST CKT SYMBOL MIN. TYP. MAX. UNIT Output Voltage SS6642-27G VIN=1.8V SS6642-30G VIN=1.8V SS6642-33G VIN=2.0V SS6642-37G VIN=2.0V SS6642-45G VIN=3.0V SS6642-50G VIN=3.0V

1 VOUT

2.633 2.925 3.218 3.607 4.387 4.875 2.700 3.000 3.300 3.700 4.500 5.000 2.767 3.075 3.382 3.792 4.613 5.125 V Start-Up Voltage IOUT=1mA, VIN:0→2V 1 VSTART 0.8 0.9 V Min. Hold-on Voltage IOUT=1mA, VIN:2→0V 1 VHOLD 0.7 V No-Load Input Current IOUT=0mA 1 IIN 15 µA Supply Current SS6642-27G SS6642-30G SS6642-33G SS6642-37G SS6642-45G SS6642-50G VS=VOUT x 0.95 Measurement of the IC input current (VOUT pin)

2 IS1

µA Supply Current SS6642-27G SS6642-30G SS6642-33G SS6642-37G SS6642-45G SS6642-50G VS=VOUT + 0.5V Measurement of the IC in- put current (VOUT pin)

2 IS2

µA SW Leakage Current VSW=6V, VS=VOUT + 0.5V 2 0.5 µA

www.SiliconStandard.com 5 of 22 SS6642G 1/15/2005 Rev.2.10 ELECTRICAL CHARACTERISTICS (Continued) PARAMETER TEST CONDITIONS TEST CKT SYMBOL MIN. TYP. MAX. UNIT SW Switch-On Resis- tance SS6642-27G SS6642-30G SS6642-33G SS6642-37G SS6642-45G SS6642-50G VS=VOUT x 0.95, VSW=0.4V

2 RON

2.2 2.1 2.0 2.0 1.9 1.9 Ω Oscillator Duty Cycle VS=VOUT x 0.95 Measurement of the SW pin waveform

3 DUTY 65 75 85 %

Max. Oscillator Freq. VS=VOUT x 0.95 Measurement of the SW pin waveform

3 FOSC 80 105 130 KHz

Efficiency 1 η 85 % Note 1: Specifications are production tested at T A=25°C. Specifications over the -40°C to 8 5°C operating temperature range are assured by design, characterization and correlation with Statistical Quality Controls (SQC). TYPICAL PERFORMANCE CHARACTERISTICS Test circuit refer to typical application circuit Capacitor (C2) : 47 µ F (Tantalum Type) Diode (D1) : 1N5819 Schottky Type Fig. 4 SS6642-27 Load Regulation (L=100µH CD54) 0 20 40 60 80 100 120 140 160 180 2.2 2.3 2.4 2.5 2.6 2.7 2.8 VIN=2.0VVIN=1.8VVIN=1.5V VIN=1.2V VIN=0.9V Output Voltage (V) Output Current (mA) Fig. 5 SS6642-27 Efficiency (L=100µH CD54) 0 20 40 60 80 100 120 140 160 180 VIN=2.0V VIN=1.8V VIN=1.5V VIN=1.2V VIN=0.9V Efficiency (%) Output current (mA)

www.SiliconStandard.com 6 of 22 SS6642G 1/15/2005 Rev.2.10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 6 SS6642-27 Load Regulation (L=47µH CD54) 0 20 40 60 80 100 120 140 160 180 200 220 2402.3 2.4 2.5 2.6 2.7 2.8 VIN=2.0V VIN=1.8V VIN=1.5V VIN=1.2V VIN=0.9V Output Voltage (V) Output Current (mA) 240 Fig. 7 SS6642-27 Efficiency (L=47µH CD54) Efficiency (%) Output current (mA) 0 20 40 60 80 100 120 140 160 180 200 220 VIN=2.0V VIN=1.8V VIN=1.5V VIN=1.2V VIN=0.9V Fig. 8 SS6642-27 Start-Up & Hold-ON Voltage (L=47 µH CD54) 0 2 4 6 8 10 12 14 16 18 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Start up Hold on Input Voltage (V) Output Current (mA) Fig. 9 SS6642-27 Start-Up & Hold-ON Voltage (L=100µH CD54) 0 2 4 6 8 10 12 14 16 180.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Start up Hold on Input Voltage (V) Output Current (mA) Fig. 10 SS6642-27 Output Voltage vs. Temperature Output Voltage (V) Temperature (°C) -40 -20 0 20 40 60 80 100 2.60 2.62 2.64 2.66 2.68 2.70 2.72 2.74 2.76 2.78 2.80 Fig. 11 SS6642-27 Switching Frequency vs. TemperatureSwitching Frequency (kHz) Temperature (°C) -40 -20 0 20 40 60 80 100 100 120 140 160

www.SiliconStandard.com 7 of 22 SS6642G 1/15/2005 Rev.2.10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 12 SS6642-27 Maximum Duty Cycle vs. Temperature Maximum Duty Cycle (%) Temperature (°C) -40 -20 0 20 40 60 80 100 Fig. 13 SS6642-27 SW Turn ON Resistance vs. Temperature SW Turn ON Resistance (Ω) Temperature (°C) -40 -20 0 20 40 60 80 100 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 Fig. 14 SS6642-27 Supply Current vs. Temperature Supply Current (µA) Temperature (°C) -40 -20 0 20 40 60 80 100 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 VIN=2.0V VIN=1.8VVIN=1.5V VIN=1.2V VIN=0.9V Fig. 15 SS6642-30 Load Regulation (L=100µH, CD54) Output voltage VOUT(V) Output Current (mA) 0 20 40 60 80 100 120 140 160 180 VIN=2.0 VIN=1.8V VIN=1.5V VIN=1.2V VIN=0.9V Fig. 16 SS6642-30 Efficiency (L=100µH, CD54) Efficiency (%) Output Current (mA) Fig. 17 SS6642-30 Load Regulation (L=47µH CD54) 0 20 40 60 80 100 120 140 160 180 200 220 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 VIN=2.0VVIN=1.8VVIN=1.5V VIN=1.2V VIN=0.9V Output Voltage (V) Output Current (mA)

www.SiliconStandard.com 8 of 22 SS6642G 1/15/2005 Rev.2.10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 225 Fig. 18 SS6642-30 Efficiency (L=47 µH CD54) 0 25 50 75 100 125 150 175 200 50 VIN=2.0V VIN=1.8V VIN=1.5V VIN=1.2V VIN=0.9V Efficiency (%) Output Current (mA) 0 2 4 6 8 10 12 14 16 18 20 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Fig. 19 SS6642-30 Start-up & Hold-on Voltage (L=100µH CD54) Start up Hold on Input Voltage (V) Output Current (mA) 0 2 4 6 8 10 12 14 16 18 20 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Fig. 20 SS6642-30 Start-up & Hold-on Voltage (L=47 µH CD54) Start up Hold on Input Voltage (V) Output Current (mA) Fig. 22 SS6642-30 Switching Frequency vs. Temperature Switching Frequency (kHz) Temperature (°C) -40 -20 0 20 40 60 80 100 100 120 140 160 Fig. 23 SS6642-30 Maximum Duty Cycle vs. Temperature Maximum Duty Cycle (%) Temperature (°C) -40 -20 0 20 40 60 80 100 Fig. 21 SS6642-30 Output Voltage vs. Temperature Output Voltage (V) Temperature (°C) -40 -20 0 20 40 60 80 100 2.90 2.92 2.94 2.96 2.98 3.00 3.02 3.04 3.06 3.08 3.10 No Load

www.SiliconStandard.com 9 of 22 SS6642G 1/15/2005 Rev.2.10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 24 SS6642-30 SW Turn ON Resistance vs. TemperatureSW Turn ON Resistance (Ω) Temperature (°C) -40 -20 0 20 40 60 80 100 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 Fig. 25 SS6642-30 Supply Current vs. Temperature Supply Current (µA) Temperature (°C) -40 -20 0 20 40 60 80 100 0 25 50 75 100 125 150 175 200 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 VIN=2.0V VIN=1.8V VIN=1.5V VIN=1.2V VIN=0.9V Fig. 26 SS6642-33 Load Regulation (L=100µH, CD54) Output Voltage (V) Output Current (mA) 0 25 50 75 100 125 150 175 200 VIN=2.0V VIN=1.8V VIN=1.5V VIN=1.2V VIN=0.9V Fig. 27 SS6642-33 Efficiency (L=100µH, CD54) Efficiency (%) Output Current (mA) 0 25 50 75 100 125 150 175 200 225 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 Fig. 28 SS6642-33 Load Regulation (L=47 µH, CD54) VIN=2.0VVIN=1.8V VIN=1.5V VIN=1.2V VIN=0.9V Output Voltage (V) Output Current (mA) 0 25 50 75 100 125 150 175 200 225 250 VIN=2.0V VIN=1.8V VIN=1.5V VIN=1.2V VIN=0.9V Fig. 29 SS6642-33 Efficiency (L=47 µH,CD54) Efficiency (%) Output Current (mA)

www.SiliconStandard.com 10 of 22 SS6642G 1/15/2005 Rev.2.10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) 0 2 4 6 8 10 12 14 16 18 20 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 Fig. 30 SS6642-33 Start-up & Hold-on Voltage (L=100µH CD54) Start up Hold on Input Voltage (V) Output Current (mA) Fig. 31 SS6642-33 Output Voltage vs. Temperature Output Voltage Vout (V) Temperature (°C) -40 -20 0 20 40 60 80 100 3.00 3.05 3.10 3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 No Load Fig. 32 SS6642-33 Switching Frequency vs. TemperatureSwitching Frequency (kHz) Temperature (°C) -40 -20 0 20 40 60 80 100 100 120 140 160 Fig. 33 SS6642-33 Maximum Duty Cycle vs. TemperatureMaximum Duty Cycle (%) Temperature (°C) -40 -20 0 20 40 60 80 100 Fig. 34 SS6642-33 SW Turn ON Resistance vs. TemperatureSW Turn ON Resistance (Ω) Temperature (°C) -40 -20 0 20 40 60 80 100 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 Fig. 35 SS6642-33 Supply Current vs. Temperature Supply Current IDD1 (µA) Temperature (°C) -40 -20 0 20 40 60 80 100

www.SiliconStandard.com 11 of 22 SS6642G 1/15/2005 Rev.2.10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 36 SS6642-37 Load Regulation (L=100 µH) Output Voltage (V) Output Current (mA) 0 25 50 75 100 125 150 175 200 225 250 275 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 VIN=2.5V VIN =2.0VVIN=1.8V VIN=1.2V VIN =0.9V Fig. 37 SS6642-37 Efficiency (100µH) Efficiency (%) Output Current (mA) 0 25 50 75 100 125 150 175 200 225 250 VIN =2.5V VIN=2.0V VIN=1.8V VIN=1.2V VIN=0.9V Fig. 38 SS6642-37 Load Regulation (L=47 µH) Output Voltage (V) Output Current (mA) 0 25 50 75 100 125 150 175 200 225 250 275 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 VIN=2.5V VIN=2.0VVIN=1.8V VIN=1.2V VIN=0.9V Fig. 39 SS6642-37 Efficiency (47µH) Efficiency (%) Output Current (mA) 0 25 50 75 100 125 150 175 200 225 250 275 VIN=2.5V VIN=2.0VVIN=1.8V VIN=1.2VVIN=0.9V Fig. 40 SS6642-37 Start-up & Hold-on Voltage (L=100 µH) Input Voltage (V) Output Current (mA) 0 5 10 15 20 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Hold on Start up Fig. 41 SS6642-37 Output Voltage vs. Temperature Output Voltage (V) Temperature (°C) -40 -20 0 20 40 60 80 100 3.40 3.45 3.50 3.55 3.60 3.65 3.70 3.75 3.80 3.85 3.90 3.95 4.00 No Load

www.SiliconStandard.com 12 of 22 SS6642G 1/15/2005 Rev.2.10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 42 SS6642-37 Switching Frequency vs. Temperature Switching Frequency (KHz) Temperature (°C) -40 -20 0 20 40 60 80 100 100 120 140 160 Fig. 43 SS6642-37 Maximum Duty Cycle vs Temperature Maximum Duty Cycle (%) Temperature (°C) -40 -20 0 20 40 60 80 100 Fig. 44 SS6642-45 Load Regulation (L=100 µH) Output Voltage (V) Output Current (mA) 0 50 100 150 200 250 300 350 400 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 VIN=3.0V VIN=1.5V VIN=2.0V VIN=1.2V VIN=0.9V Fig. 45 SS6642-45 Efficiency (L=100µH) Efficiency (%) Output Current (mA) 0 50 100 150 200 250 300 350 400 VIN=3.0V VIN=1.5V VIN=2.0V VIN=1.2V VIN=0.9V Fig. 46 SS6642-45 Load Regulation (L=100 µH) Output Voltage (V) Output Current (mA) 0 50 100 150 200 250 300 350 400 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 VIN=3.0V VIN=1.5V VIN=2.0V VIN=1.2V VIN=0.9V Fig. 47 SS6642 -45 Start-up & Hold-On Voltage (L=100µH) Input Voltage (V) Output Current (mA) 0 5 10 15 20 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Hold on Start up

www.SiliconStandard.com 13 of 22 SS6642G 1/15/2005 Rev.2.10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 48 SS6642-45 Output Voltage vs. Temperature Output Voltage (V) Temperature (°C) -40 -20 0 20 40 60 80 100 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 No Load Fig. 49 SS6642- 45 Supply Current vs. Temperature Supply Current (µA) Temperature (°C) -40 -20 0 20 40 60 80 100 Fig. 50 SS6642 -45 Switching Frequency vs. Temperature Switching Frequency (kHz) Temperature (°C) -40 -20 0 20 40 60 80 100 100 120 140 160 Fig. 51 SS6642-45 Maximum Duty Cycle vs. Temperature Maximum Duty Cycle (%) Temperature (°C) -40 -20 0 20 40 60 80 100 Fig. 52 SS6642-45 SW Tu rn ON Resistance vs. Temperature SW Turn ON Resistance (Ω) Temperature (°C) -40 -20 0 20 40 60 80 100 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 0 50 100 150 200 250 300 350 400 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIN=1.2V VIN=3.0V VIN=2.0V VIN=1.5V VIN=0.9V Fig. 53 SS6642-50 Load Regulation ( L=100µH CD54) Output Voltage (V) Output Current (mA)

www.SiliconStandard.com 14 of 22 SS6642G 1/15/2005 Rev.2.10 0 50 100 150 200 250 300 350 400 100 VIN=1.2V Fig. 54 SS6642-50 Efficiency (L=100 µH CD54) VIN=3.0V VIN=2.0V VIN=1.5V VIN=0.9V Efficiency (%) Output Current (mA) 0 50 100 150 200 250 300 350 400 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Fig. 55 SS6642-50 Load Regulation (L=47µH CD54) VIN=1.2V VIN=3.0V VIN=2.0V VIN=1.5V VIN=0.9V Output Voltage (V) Output Current (mA) 0 50 100 150 200 250 300 350 400 Fig. 56 SS6642-50 Efficiency (L=47 µH CD54) Efficiency (%) Output Current (mA) VIN=1.2V VIN=3.0V VIN=2.0V VIN=1.5V VIN=0.9V 0 2 4 6 8 10 12 14 16 18 20 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 Fig. 57 SS6642-50 Start-up & Hold-on Voltage (L=100µH CD50) Input Voltage (V) Output Current (mA) Start up Hold on TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 58 SS6642-50 Output Voltage vs. Temperature Output Voltage VOUT (V) Temperature (°C) -40 -20 0 20 40 60 80 100 4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 No Load Fig. 59 SS6642-50 Switching Frequency vs. Temperature Switching Frequency (kHz) Temperature (°C) -40 -20 0 20 40 60 80 100 100 120 140 160

www.SiliconStandard.com 15 of 22 SS6642G 1/15/2005 Rev.2.10 TYPICAL PERFORMANCE CHARACTERISTICS (Continued) Fig. 60 SS6642-50 Maximum Duty Cycle vs. Temperature Maximum Duty Cycle (%) Temperature (°C) -40 -20 0 20 40 60 80 100 Fig. 61 SS6642-50 SW Turn ON Resistance vs. Temperature SW Turn ON Resistance (Ω) Temperature (°C) -40 -20 0 20 40 60 80 100 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 -40 -20 0 20 40 60 80 100 100 Fig. 62 SS6642-50 Supply Current vs. Temperature Supply Current IDD1 (µA) Temperature (°C) VOUT 50mV/div Load Step 50mA/div Fig. 63 Load Transient Response (L1=100µH, C2=47µF, VIN=2V) 10mA VOUT 20mv/div VIN 0.5V/div Fig. 64 Line Transient Response (L 1=100µH, C2=47µF)

www.SiliconStandard.com 16 of 22 SS6642G 1/15/2005 Rev.2.10 BLOCK DIAGRAM GND VOUT SW 1.25V REF. Enable OSC, 100KHz PIN DESCRIPTIONS PIN 1 : GND - Ground. Must be low impedance; solder directly to ground plane. PIN 2 : VOUT - IC supply pin. Connect VOUT to the regulator output. PIN 3 : SW –Drain of the internal N-channel MOSFET switch.

www.SiliconStandard.com 17 of 22 SS6642G 1/15/2005 Rev.2.10

APPLICATION INFORMATION

The SS6642G PFM (pulse frequency modulation) controller IC combines a switch-mode regulator, N- channel power MOSFET, precision voltage refer- ence, and voltage detector in a single monolithic device. It offers extremely low quiescient current, high efficiency, and very low gate threshold voltage to ensure start-up with low battery voltage (0.8V typ.). Designed to maximize battery life in portable products, it minimizes switching losses by only switching as needed to service the load. PFM controllers transfer a discrete amount of en- ergy per cycle and regulat e the output voltage by modulating the switching frequency with a constant turn-on time. Switching frequency depends on load, input voltage, and inductor value, and it can range up to 100KHz. The SW on-resistance is typically 1.9 to 2.2Ω to minimize switch losses. When the output voltage drops, the error comparator enables the 100kHz oscillator that turns on the MOSFET for around 7.5us and off for 2.5us. Turning on the MOSFET allows inductor current to ramp up, storing energy in a magnetic field. When the MOSFET turns off, inductor current is forced through the diode to the output capacitor and l oad. As the stored energy is depleted, the current ramps down until the diode turns off. At this point, the inductor may ring due to residual energy and stray capacitance. The output capacitor stores charge when the current flowing through the diode is high, and releases it when the current is low, thereby maintaining a steady voltage across the load. As the load increases, the output capacitor dis- charges faster and the error comparator initiates cycles sooner, increasing the switching frequency. The maximum duty cycle ensures adequate time for energy transfer to the output during the second half of each cycle. Depending on the circuit, a PFM controller can operate in either discontinuous mode or continuous conduction mode. Continuous conduction mode means that the inductor current does not ramp down to zero during each cycle. VIN SW VOUT EXT ID IOUT Isw Ico IIN IPK IIN VEXT ISW IOUT TDIS Charge Co. VSW Discharge Co. ID t Discontinuous Conduction Mode

www.SiliconStandard.com 18 of 22 SS6642G 1/15/2005 Rev.2.10 IPK IIN VEXT ISW IOUT VSW ID t Continuous Conduction Mode In the continuous mode, the switching fre- quency is ( ) − + − +≅ − + − + − += SW DOUT IN DOUT ON SW DOUT SWIN SW DOUT IN DOUT ON SW V V V V V V T )]V V V V V(2 x[1 * ) V V (V V V V T where Vsw = switch drop and is proportional to output current. Inductor Selection To operate as an efficient energy transfer ele- ment, the inductor must fulfill three require- ments. First, the inductance must be low enough for the inductor to store adequate en- ergy under the worst-case condition of mini- mum input voltage and switch ON time. Second, the inductance must also be high enough so that the maximum current rating of the SS6642 and the inductor are not exceeded at the other worst- case condition of maximum input voltage and ON time. Lastly, the inductor must have sufficiently low DC resistance so excessive power is not lost as heat in the windings. Unfortunately, this is inversely related to physical size. Continuous Conduction Mode At the boundary between continuous and dis- continuous modes, output current (IOB) is deter- mined by Minimum and maximum input voltage, output voltage and output current must be established in advance and then the inductor can be selected. ) x 1 ( * T *L V*2 1*V VI ON IN OUT IN OB − In discontinuous mode operation, at the end of the switch ON time, peak current and energy in the inductor build according to where Vd is the diode drop, L T* ) R R ( x ON S ON+ =  +− − += ) T *L Rs RONexp( 1 *Rs R VI ON ON IN PK RON= Switch turn-on resistance, R S= Inductor DC resistance ()   − ≅ 2 x1 * T *L V ON IN TON = Switch ON time In the discontinuous mode, the switching fre- quency (Fsw) is ON IN TL V≅ (simple loss equation), Fsw = ) x (1 T V 2ON2IN OUTIN DOUT − + where L T* ) R R ( x ON S ON+ =

www.SiliconStandard.com 19 of 22 SS6642G 1/15/2005 Rev.2.10 EL = 2Ipk L2 1 ×  −  −+  − − += x1 * T * V VI * x V V V V VI ON SW IN OUT SW IN SW D OUT PK The power supplied by the inductor per cycle must be equal to or greater than Valley current (Iv) is )fsw 1( * ) (I * ) V V (V /f POUTIN DOUTSW L − + =  −  −−  −− − += 2 x1 * T *2L VSW VI *2 x VSW V V V VI ON IN OUT IN SW D OUT V in order for the converter to regulate the output. When loading is over IOB, the PFM controller operates in continuous mode. Inductor peak current can be derived from Table 1 Indicates resistance and height for each coil. Power Inductor Type Inductance ( µH ) Resistance ( Ω ) Rated Current (A) Height (mm) 22 0.10 0.7 47 0.18 0.5 DS1608 100 0.38 0.3 2.9 22 0.08 2.7 Coilcraft SMT Type (www.coilcraft.com) DO3316 47 0.14 1.8 5.2 47 0.25 0.7 Sumida SMT Type CD54 100 0.50 0.5 4.5 47 0.25 0.7 Hold SMT Type PM54 100 0.50 0.5 4.5 Hold SMT Type PM75 33 0.11 1.2 5.0 Capacitor Selection Most of the input supply is applied to the input bypass capacitor, so the capacitor voltage rating should be at least 1.25 times greater than the maximum input voltage. A poor choice for an output capacitor can result in poor efficiency and high output ripple. Ordinary aluminum electrolytic s, while inexpensive may have unacceptably poor ESR and ESL. There are low -ESR aluminum capacitors for switch mode DC-DC converters which work much better than general types. Tantalum capacitors provide still better performance but are more expensive. OSCON capacitors have extremely low ESR and small size. If capacitance is reduced, output rip- ple will increase. Diode Selection Speed, forward drop, and leakage current are the three main considerations in selecting a rectifier diode. Best performance is obtained with Schottky rectifier diodes such as the 1N5819. SSC also has Schottkies for surface-mount. For lower output power a 1N4148 can be used , although efficiency and start-up voltage will suffer substantially.

www.SiliconStandard.com 20 of 22 SS6642G 1/15/2005 Rev.2.10 Component Power Dissipation Operating in discontinuous mode, power loss in the winding resistance of the inductor can be approximated to () ()OUT OUT FOUT D ON L P *V V V* R *L T 2PD   + where POUT=VOUT * IOUT; RS=Inductor DC R; VD = Diode drop. The power dissipated in the MOSFET switch is () ()OUT OUT IN DOUT ON ON SW P *V V V V* R *L T 2PD   − + The power dissipated in the rectifier diode is ()OUT OUT D P *V VPDd 

www.SiliconStandard.com 21 of 22 SS6642G 1/15/2005 Rev.2.10 PHYSICAL DIMENSIONS (unit: mm) SOT-23 (GU) SYMBOL MIN MAX A 0.95 1.45 A1 0.05 0.15 A2 0.90 1.30 b 0.30 0.50 c 0.08 0.22 D 2.80 3.00 E 2.60 3.00 E1 1.50 1.70 e 0.95 BSC e1 1.90 BSC L 0.30 0.60 L1 0.60 REF E D e A A2 b 0.25 L θ c θ 0˚ 8 ˚ SOT-89 (GX) SYMBOL MIN MAX A 1.40 1.60 B 0.44 0.56 B1 0.36 0.48 C 0.35 0.44 D 4.40 4.60 D1 1.50 1.83 E 2.29 2.60 e 1.50 BSC e1 3.00 BSC H 3.94 4.25 e H D A C L E B L 0.89 1.20 All package options are Pb-free, RoHS compliant.

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