LTC1147 Linear Technology, LTC1147 Datasheet - Page 5

• Manufacturer Part Number: LTC1147
• Description: High Efficiency Step-Down Switching Regulator Controllers
• Manufacturer: Linear Technology

FU CTIO AL DIAGRA
PI FU CTIO S
V
to ground Pin 7.
C
the operating frequency. The actual frequency is also
dependent upon the input voltage.
I
comparator threshold increases with the Pin 3 voltage.
SENSE
which sets the output voltage. Pin 4 is also the (–) input for
the current comparator.
SENSE
A built-in offset between Pins 4 and 5 in conjunction with
R
TH
IN
T
SENSE
U
(Pin 2): External capacitor C
U
(Pin 1): Main Supply Pin. Must be closely decoupled
(Pin 3): Gain Amplifier Decoupling Point. The current
SLEEP
–
+
sets the current trip threshold.
(Pin 5): The (+) input to the current comparator.
(Pin 4): Connects to internal resistive divider
U
S
U
+
–
V
TH2
U
C
2
T
V
TH1
T
from Pin 2 to ground sets
–
+
Q
W
OFF-TIME
CONTROL
T
R
S
Pin 6 Connection Shown For LTC1147-3.3 and LTC1147-5; Changes Create LTC1147L.
V
SENSE
IN
–
1
8
7
SHDN/V
versions of the LTC1147 family operate normally. Pulling
Pin 6 high holds the P-channel MOSFET off and puts the
LTC1147 in micropower shutdown mode. Requires CMOS
logic signal with t
On the LTC1147L this pin serves as the feedback pin from
an external resistive divider used to set the output voltage.
GND (Pin 7): Two independent ground lines must be
routed separately to: 1) the (–) terminal of C
cathode of the Schottky diode and (–) terminal of C
PDRIVE (Pin 8): High current drive for the P-channel
MOSFET. Voltage swing at this pin is from V
C
V
PDRIVE
GND
IN
I
TH
–
+
3
25mV TO 150mV
–
FB
(Pin 6): When grounded, the fixed output
+
13k
SHDN
LTC1147-5/LTC1147L
r
, t
6
f
< 1 s. Do not leave this pin floating.
V
G
–
+
–
+
REFERENCE
SENSE
1.25V
5
LTC1147-3.3
V
OS
+
V
FB
6
OUT
SENSE
IN
LTC1147 • FD
4
, and 2) the
to ground.
100k
–
5pF
IN
5
.