5
LTC1148
LTC1148-3.3/LTC1148-5
114835fd
CCHARA TERIST
ICS
UW
AT
Y
P
I
CA
LPER
F
O
R
C
E
Current Sense Threshold Voltage
TEMPERATURE (°C)
0
0
SENSE VOLTAGE (mV)
25
50
75
175
125
20
40
150
100
60
80
100
MAXIMUM
THRESHOLD
MINIMUM
THRESHOLD
LTC1148 • TPC09
Off Time vs V
OUT
OUTPUT VOLTAGE (V)
0
OFF TIME (µs)
40
50
60
4
LTC1148 • TPC08
30
20
0
1
23
10
80
70
5
LTC1148-5
LTC1148-3.3
V
SENSE
–
= V
OUT
Gate Charge Supply Current
OPERATING FREQUENCY (kHz)
20
0
GATE CHARGE CURRENT (mA)
4
8
12
28
20
80
140
24
16
200
260
Q
N
+ Q
P
= 100nC
Q
N
+ Q
P
= 50nC
LTC1148 • TPC07
P-DRIVE (Pin 1): High Current Drive for Top P-Channel
MOSFET. Voltage swing at this pin is from V
IN
to ground.
NC (Pin 2): No Connection. Can connect to power ground.
V
IN
(Pin 3): Main Supply Pin. Must be closely decoupled
to power ground Pin 12.
C
T
(Pin 4): External capacitor C
T
from Pin 4 to ground sets
the operating frequency. The actual frequency is also
dependent upon the input voltage.
INTV
CC
(Pin 5): Internal Supply Voltage, Nominally 3.3V.
Can be decoupled to signal ground. Do not externally load
this pin.
I
TH
(Pin 6): Gain Amplifier Decoupling Point. The current
comparator threshold increases with the Pin 6 voltage.
SENSE
–
(Pin 7): Connects to internal resistive divider
which sets the output voltage in LTC1148-3.3 and
LTC1148-5 versions. Pin 7 is also the (–) input for the
current comparator.
SENSE
+
(Pin 8): The (+) Input to the Current Comparator.
A built-in offset between Pins 7 and 8 in conjunction with
R
SENSE
sets the current trip threshold.
V
FB
(Pin 9): For the LTC1148 adjustable version, Pin 9
serves as the feedback pin from an external resistive
divider used to set the output voltage. On LTC1148-3.3
and LTC1148-5 versions this pin is not used.
SHUTDOWN (Pin 10): When grounded, the LTC1148
series operates normally. Pulling Pin 10 high holds both
MOSFETs off and puts the LTC1148 series in micropower
shutdown mode. Requires CMOS logic signal with t
R
,
t
F
< 1µs, should not be left floating.
SGND (Pin 11): Small-Signal Ground. Must be routed
separately from other grounds to the (–) terminal of C
OUT
.
PGND (Pin 12): Driver Power Ground. Connects to source
of N-channel MOSFET and the (–) terminal of C
IN
.
NC (Pin 13): No Connection. Can connect to power ground.
N-DRIVE (Pin 14): High Current Drive for Bottom
N-Channel MOSFET. Voltage swing at Pin 14 is from
ground to V
IN
.
PI FU CTIO S
U
UU