L6714 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
L6714
STMicroelectronics
'L6714' PDF : 70 Pages View PDF
L6714
17
Maximum Duty-cycle limitation
Maximum Duty-cycle limitation
The device limits the maximum duty cycle and this value is not fixed but it depends on the
delivered current given by the following relationship:
D(max)
=
0.80 – (IDROOP ×
2.857 k )
=
0.80
–
⎛
⎝
R-----S----E---N----S---E--
Rg
×
I×
OUT
2.857k⎠⎞
From the previous relationships the maximum duty cycle results:
⎧80%
D(max) = ⎩⎨40%
IDROOP = 0µA
IDROOP = 140µA
If the desired output characteristic crosses the limited-DMAX maximum output voltage, the
output resulting voltage will start to drop after the cross-point. In this case the output voltage
starts to decrease following the resulting characteristic (dotted in Figure 19) until UVP is
detected or anyway until IDROOP=140µA.
Figure 19. Maximum Duty-Cycle (left) and limited DMAX output voltage (right)
DMAX
80 %
40 %
Maximum Duty Cycle
IDROOP = 140µA
(IOCP = N x IOCPx )
IDROOP
VOUT
0.80 VIN
Limited DMAX Output Voltage
0.40 VIN
Limted-DMAX Output Char.
Desired output Char.
Resulting Output Char.
UVP Threshold
IOCP = N x IOCPx
(IDROOP = 140µA)
IOUT
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