SP6122_04 Datasheet, PDF(17/19 Page) Sipex Corporation – Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters

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SP6122_04 Datasheet, PDF (17/19 Pages) Sipex Corporation – Low Voltage, Micro 8, PFET, Buck Controller Ideal for 1A to 5A, Small Footprint, DC-DC Power Converters

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SP6122 Design Calculator Example: Evaluation Board with 3.3VIN, 1.9VOUT

Table 2, SP6122 Design Calculator, illus-

trates the calculations and formulas con-

tained in the Sipex Non-Synchronous Buck

Cad Calculator spreadsheet, (available in

the applications section of the Sipex website

at www.sipex.com). The example shown is

the same SP6122 Evaluation Board used

previously with VIN = 3.3V, VOUT = 1.9V at

4A. As you can see, the SP6122 efficiency

at 4A output is calculated to be 84.3%.

Compare this with the Typical Performance

Characteristics curve of 84.5%, which is

very close considering the tolerances of

various components, and you see how use-

ful this easy design calculator is to evaluate

your SP6122 designs.

SP6122 Non-Synchronous Buck Design Calculator

STEADY STATE CALCULATION

Enter Values

VIN = Input Voltage (V)

VOUT = Output Voltage (V)

Fs = Switching Frequency (kHz)

IOUT = Load Current (A)

L = Inductance (ÂµH)

ESRin = Input Capacitor ESR (mâ¦)

CIN = Input Capacitance (ÂµF)

ESROUT = Output Capacitor ESR (â¦)

Calculation Results

Formula

3.3 D = Duty Cycle

1.9 Iripple = Ripple Current (A)

300 Ipeak = Peak Inductor Current (A)

4 Output Ripple (mV)

0.58 = VOUT/VIN

1.22 = (VIN-VOUT)*VOUT/(Fs*1000*L*0.000001*VIN)

4.61 = IOUT+Iripple/2

42.75 = Iripple*ESRout

2.2 Iin = Max Input Current (A)

2.56 = IOUT*D/0.9

5 Max Input Ripple (mV)

96.99 = IOUT*ESRin+Iin*(1-D)/(Fs*CIN*0.000001)

47 Iin_rms = Input Cap RMS Current (A) 1.98 = IOUT*SQRT(D*(1-D))

EFFICIENCY CALCULATION

Enter Values

Calculation Results

Formula

RGH = GH Impedance (â¦)

PMOS

4 Pic = IC Power (switching) (mW)

31.35 = Icc*VIN+Chs*VIN*Fs*0.001

TRISE = SP6122 typ. PMOS rise time (ns) 20 Psch = Schottky Conducting Loss (mw) 848.48 = Vf*IOUT*(1-D)*1000

TFALL = SP6122 typ. PMOS rise time (ns) 40

Chs = PMOS Gate Charge @ VIN (nc)

15 Pch = PMOS Conducting Loss (mW) 202.67 = IOUT*IOUT*D*Rhs

Rhs = RDS(ON) @ VIN (mâ¦)

22 Psh = PMOS Switching Loss (mW)

118.80 = 1/2*IOUT*VIN*(TRISE+TFALL)*Fs*0.001

Phs = Total PMOS Loss (mW)

321.47 = Pch + Psh

Vf = Schottky Forward Voltage

ICC = Supply Current (no switch) (mA)

ESR_L = Inductor ESR (mâ¦)

0.5 Pl = Inductor loss (mW)

5 PcIN = Input Capacitor Loss(mW)

12 Pltot = Total Power Losses (mW)

192.00 = IOUT*IOUT*ESR_L

19.54 = ESRIN*Iin_rms*Iin_rms

1412.84 = Pic+Pls+Phs+Pl+Psch

Efficiency (%)

84.32 = VOUT*IOUT/(VOUT*IOUT - Pltot/1000)*100

Table 2: Design Calculator

Date: 10/02/04

SP6122 Low Voltage, Micro 8, PFET, Buck Controller

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