# Meka

From DIDEAS Wiki

## For larger but thermally safer design

- IRF FETs >=75V, low Rds ON, dpak
- IRLR3110ZPBF top IRF choice. 100V, 14mohm, 34nC, 1.05C/watt : Available from IRF <$2/each DS

## For smallest design - Renesas LFPAK devices

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- HAT2174H, 100V, 27mOhm, 33nC-2280 pF, 6.25C/W
- HAT2175H, 100V, 42mOhm, 21nC-1445 pF, 8.34C/W

- Estimated power dissipation for HAT2175H

Fsw (switching freq) 100kKz Td (dead time) = 100nS Ts (switching time) = 50nS I (current) 6amps Vd (diode drop) = 1.1V Vsup (supply voltage) = 60V R (turn on resistance) = 42mohm

Pr = I^2 * R = 1.5W Pd = I * Vd * Td * f = 0.066W Ps = I * Vsup/2 *Ts * f = 0.9W

Ploss = Pr + Pd + Ps = 2.5W

Temperature of junction overcase = 2.5 * 8.4 = 21C

Gate drive current : I = Q*f/t = 21nC * 100e3 = 2.1mA, 4.2mA for 2 fets (50mW)

- For HAT2174H

Ts (switching time) = 55nS R (turn on resistance) = 21mohm Ploss = 0.75 + 0.06 + 1.1 = 1.9W

Temperature of junction overcase = 1.9 * 6.3 = 12C

Gate drive current : I = Q*f/t = 33nC * 100e3 = 3.3mA, 6.6mA for 2 fets (80mW)

## Ripple Voltage

- dV = I dT / C
- dT = 9.5uS max at 100 KHz
- I = 6 amps max
- for C=25uF, dV = 2.3V