MCR03EZPFX1002 datasheet(16/32 Pages) IRF

16 / 32 page

Rev 16.0

PD-97660

IR3831WMPbF

Minimum on time Considerations

The minimum ON time is the shortest amount of

time for which the Control FET may be reliably

turned on, and this depends on the internal

timing delays. For the IR3831W, the typical

minimum on-time is specified as 50 ns.

Any design or application using the IR3831W

must ensure operation with a pulse width that is

higher than this minimum on-time and preferably

higher than 100 ns. This is necessary for the

circuit to operate without jitter and pulse-

skipping, which can cause high inductor current

ripple and high output voltage ripple.

In any application that uses the IR3831W, the

following condition must be satisfied:

The minimum output voltage for the IR3831W is

limited to V

out(min) = 0.6 V.

Furthermore, for the IR3831W, especially for

active bus termination applications, it is strongly

recommended to use a switching frequency of

400 kHz to obtain clean and jitter free operation

in sourcing as well as sinking modes. Therefore,

the maximum input voltage that may be stepped

down to 0.6V at 400 kHz without jitter or pulse

skipping is 15 V.

V/s

100

0.6

(min)

≤

∴

≤

∴

out

Maximum Duty Ratio Considerations

A fixed off-time of 200 ns maximum is specified

for the IR3831W. This provides an upper limit on

the operating duty ratio at any given switching

frequency. It is clear, that higher the switching

frequency, the lower is the maximum duty ratio at

which the IR3831W can operate. To allow a

margin of 50ns, the maximum operating duty

ratio in any application using the IR3831W

should still accommodate about 250 ns off-time.

Fig 9. shows a plot of the maximum duty ratio v/s

the switching frequency, with 250 ns off-time.

out

Vin ×

(min)

out

≤

∴

≤

∴

≤

Fig. 9. Maximum duty cycle v/s switching

frequency.

M ax Duty Cycle

250

450

650

850

1050

1250

1450

1650

S w itching Frequency (kH z )

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