MB3828 查看數據表（PDF） - Fujitsu

零件编号

产品描述 (功能)

比赛名单

MB3828

Pentium® DC/DC Converter IC

Fujitsu 

MB3828

s METHOD OF SETTING THE SOFT START TIME

At startup of the MB3828, the capacitor (CS) connected to the CS pin begins charging. This produces a soft

start, by providing output voltage from Error Amp. that is proportional to the CS pin voltage regardless of the

DC/DC converter load current.

Soft start time (time to output setting voltage VD)

tS (sec) ~ VD × CS (µF)

2 (µA)

s TIME SETTING BY SHORT DETECTION

When load conditions change rapidly with the reduced output voltage, as when a load fault occurs, the Capacitor

Cscp connected to the CSCP pin (pin 22) is charged to threshold voltage (VTH:=0.68V) and sets a latch, the

external FET is turned off (inactive interval 100%).

Short detection time

tPE (sec) ~ 0.68 × CSCP (µF) / 2 (µA)

s OSCILLATOR FREQUENCY SETTING

The oscillator frequency can be set by connecting resistance to the RT pin (pin 1).

Oscillator frequency

fOSC (kHz) ~ 26250 / RT (kΩ)

s METHOD OF SETTING THE DISCHARGE TIME

• An “L” level CTL signal while the ENB pin is set to “H” level causes the resistance (RS) connected to the RS

pin to discharge electrical charge the capacitor (CS) connected to the CS pin, causing the output voltage to

fall gradually regardless of the DC/DC converter load current.

Discharge time (time to 0.05 V output voltage)

toff (msec) ~ RS (kΩ) × CS (µF) × ln ( VD )

VTH (CS COMP)

• As long as the ENB pin is set to “L” level, the discharge control function is switched OFF.

s D/A BLOCK VD4 to VD0 SWITCHING

• Switching of the VD4 to VD0 pin signal during the MB3828 operation may cause transient fluctuation in output

voltage from the DC/DC converter. The resulting voltage instability may cause an “L” level from the PWRGOOD

block, activating the OVP protection and shutting off the output from the DC/DC converter.

To switch VD4 to VD0 pin settings, first input an “L” level control signal to the CTL pin to place the MB3828

in standby status.

• When all VD4 to VD0 pin signals are set to “H” level, the DC/DC converter output is switched OFF.

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