Datasheet

LTC4417
22
4417f
applicaTions inForMaTion
Figure 13. Industrial Hand Held Computer
electrolytic capacitors, add 20% to C
L
and for ceramic
NP0 C
S
capacitors subtract 5%.
R
S
=
(6V – 1.8V) • 120µF • 20mΩ
6.5nF • 700mV
R
S
= 2.22kΩ
(22)
The standard value of 2.21kΩ is chosen for R
S
and C
VS1
is chosen to be ten times C
S
or 68nF. Although 1.8V is a
typical value for V
GS
, there is sufficient margin – even if
V
GS
= 0V, the resulting I
DM
is lower than the 71A rating.
With R
S
and C
S
known, the desired load capacitance with
inrush current limiting is checked with Equation (14)
as shown in Equation (23). Because the required load
capacitance of 90µF is lower than the chosen load ca-
pacitor of 100µF, the initial choice of 100µF is suitable.
C
L
≥
2A •(3µs+12µs+ 0.79 • 2.21kΩ • 6.8nF)
600mV
C
L
≥ 90µF
(23)
VS1
V1 V
OUT
VALID1
VALID2
VALID3
12V SUPPLY
C
IN
2700µF
7.4V Li-Ion
BATTERY
(2 × 3.7V)
UV1
OV1
R3
806k
R2
41.2k
R1
60.4k
R6
768k
R5
53.6k
R4
113k
R9
768k
R8
53.6k
R7
113k
R10
1M
R11
1M
R12
1M
V2 INVALID
V3 INVALID
V1 INVALID
R
HYS
255k
1%
V2
UV2
OV2
V3 EN
SHDN
HYS
CAS
UV3
OV3
4417 F13
G1 VS2 VS3G2
C
VS3
0.1µF
GND
LTC4417
G3
IRF7324
M5 M6
IRF7324
M3 M4
IRF7324
M1 M2
C
VS2
0.1µF
C
VS1
68nF
C
V1
0.1µF
C
V2
0.1µF
C
V3
0.1µF
+
C
L
100µF
V
OUT
+
+
7.4V Li-Ion
BATTERY
(2 × 3.7V)
+
R
S
2.21k
D
S
BAT54
C
S
6.8nF
140k
140k