lt3724 Linear Technology Corporation, lt3724 Datasheet - Page 19

• Manufacturer Part Number: lt3724
• Description: High Voltage, Current Mode Switching Regulator Controller
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
Minimum On-Time Considerations
(Step-Down Converters)
Minimum on-time (t
the LT3724 is capable of turning the MOSFET on and then
off again. It is determined by internal timing delays and the
gate charge of the MOSFET. Applications with high input
to output differential voltages operate at low duty cycles
and may approach this minimum on-time, typically 300nS.
The LT3724 switching frequency is internally set to 200kHz,
C
R2
SS
R1
U
TG(ON)
C
R
C1
R
CSS
U
B
) is the least amount of time that
R
A
R
C
C
C2
Figure 9. LT3724 Layout Diagram (See PCB Layout Checklist).
1
3
4
5
6
7
8
W
V
SHDN
C
BURST_EN
V
V
SGND
IN
SS
FB
C
LT3724
17
SENSE
SENSE
BOOST
PGND
V
SW
U
TG
CC
+
–
16
15
14
12
11
10
9
C
VCC
C
BOOST
therefore, the minimum duty cycle of the MOSFET switch
is 6%. When the duty cycle needs to be less than 6% the
output will stay regulated, but cycle skipping may occur.
Cycle skipping results in an increase in inductor ripple
current. If it is important that cycle skipping does not
occur, follow this guideline which takes into account
worst case f
This is only an issue for supplies with V
D2
D3
V
IN(MAX)
V
IN +
M1
D1
≤ 9 • V
SW
and t
C
IN
V
L1
IN –
OUT
TG(ON)
R
SENSE
:
C
OUT
3724 F06
OUT
LT3724
< 7V.
V
+
–
OUT
19
3724fb