LTC1159CS-3.3 Linear Technology, LTC1159CS-3.3 Datasheet - Page 12

• Manufacturer Part Number: LTC1159CS-3.3
• Description: IC SW REG STEP-DOWN 3.3V 16-SOIC
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC1159CS-3.3

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 3.3V
• Current - Output: 50mA
• Frequency - Switching: 250kHz
• Voltage - Input: 4 ~ 40 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIO S I FOR ATIO
LTC1159
LTC1159-3.3/LTC1159-5
4. EXTV
supply is available in the 5V to 12V range, it may be used
to power EXTV
MOSFET gate drive requirements. There are no restrictions
on the EXTV
higher than V
absolute maximum rating.
nal supply must always be present during operation to
prevent MOSFET failure due to insufficient gate drive . The
LTC1149 family should also be considered for applications
which require the use of standard threshold MOSFETs.
Important Information About LTC1159 Adjustable
Applications
When an output voltage other than 3.3V or 5V is required,
the LTC1159 adjustable version is used with an external
resistive divider from V
regulated voltage is determined by:
The V
inductor switching node . Care should be taken to isolate
the feedback network from the inductor, and the 100pF
capacitor should be connected between the V
pins next to the package.
12
When driving standard threshold MOSFETs, the exter-
V
OUT
FB
CC
=
>3V = SHUTDOWN
pin is extremely sensitive to pickup from the
+
Connected to an External Supply. If an external
1 + R2
0V = NORMAL
IN
CC
1k
1 F
3300pF
providing EXTV
CC
R1
voltage relative to V
U
providing it is compatible with the
1.25V
0.15 F
C
390pF
OUT
T
U
to the V
Figure 6. High Efficiency Adjustable Regulator with 5.5V < V
CAP
V
V
I
C
SHDN2
TH
CC
CC
T
CC
does not exceed the 15V
LTC1159
W
V
FB
IN
IN
P-DRIVE
pin (Figure 6). The
SENSE
SENSE
N-GATE
P-GATE
EXTV
. EXTV
PGND
SGND
V
CC
FB
+
–
FB
CC
U
and SGND
may be
1N4148
VN2222LL
0.1 F
100pF
0.01 F
5M
In LTC1159N and LTC1159S applications with V
5.5V, the V
when SHDN2 is taken high, preventing shutdown. In these
applications, a pull-down must be added to the SENSE
as shown in Figure 6. This pull-down effectively takes the
place of the SHDN1 pin, ensuring complete shutdown.
Note: For versions in which both the SHDN1 and SHDN2
pins are available (LTC1159G and all fixed output ver-
sions), the two pins are simply connected to each other and
driven together to guarantee complete shutdown.
The Figure 6 circuit cannot be used to regulate a V
is greater than the maximum voltage allowed on the
LTC1159 SENSE pins (13V). In applications with V
13V, R
output capacitor and load. This operates the current sense
comparator at 0V common mode, increasing the off-time
approximately 40% and requiring the use of a smaller
timing capacitor C
Inverting Regular Applications
The LTC1159 can also be used to obtain negative output
voltages from positive inputs. In these inverting applica-
tions, the current sense resistor connects to ground while
the LTC1159 and N-channel MOSFET connections, which
would normally go to ground, instead ride on the negative
output. This allows the negative output voltage to be set by
100
100
V
IN
Si4401DY
Si4840DY
V
VALUES SHOWN FOR V
SENSE
OUT
+
= 1 + R2
CC
1N5819
pin may self-power through the SENSE pins
must be moved to the ground side of the
100 F
50V
R1
100 H
1.25
T
.
OUT
3
OUT
1
R
0.039
< 13V
SENSE
= 12V/2.5A
LTC1159 • F06
2
4
R2
215k
R1
24.9k
+
150 F
16V
OS-CON
V
OUT
OUT
OUT
which
OUT
–
pin
>
>