LTC1625IGN Linear Technology, LTC1625IGN Datasheet - Page 18

• Manufacturer Part Number: LTC1625IGN
• Description: IC SW REG STEP-DOWN SYNC 16-SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC1625IGN

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.19 ~ 36 V
• Current - Output: 50mA
• Frequency - Switching: 150kHz
• Voltage - Input: 3.7 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIONS
LTC1625
C
temperature. C
low output ripple. The output ripple in continuous mode
will be highest at the maximum input voltage and is
approximately:
The complete circuit is shown in Figure 9.
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1625. These items are also illustrated graphically in
the layout diagram of Figure 10. Check the following in
your layout:
1) Connect the TK lead directly to the drain of the topside
2) The power ground pin connects directly to the source of
18
IN
MOSFET. Then connect the drain to the (+) plate of C
This capacitor provides the AC current to the top
MOSFET.
the bottom N-channel MOSFET. Then connect the source
to the anode of the Schottky diode and (–) plate of C
which should have as short lead lengths as possible.
V
is chosen for an RMS current rating of at least 1A at
O
= ( I
L(MAX)
OUT
470pF
C
C1
)(ESR) = (0.83A)(0.033 ) = 27mV
0.1 F
is chosen with an ESR of 0.033 for
U
C
SS
10k
R
C
220pF
INFORMATION
C
INTV
C2
U
OPEN
CC
C
C
L1: SUMIDA CDRH125-150MC
IN
OUT
: AVX TPSE226M035R0300
1
2
3
4
5
6
7
8
: AVX TPSD107M010R0065
EXTV
SYNC
V
RUN/SS
FCB
I
SGND
V
TH
PROG
OSENSE
W
CC
LTC1625
Figure 9. 3.3V/2A Fixed Output at 225kHz
INTV
BOOST
PGND
V
SW
BG
TK
TG
CC
IN
U
16
15
14
13
12
11
10
9
D
CMDSH-3
IN
IN
B
.
,
0.1 F
3) The LTC1625 signal ground pin must return to the (–)
4) Keep the switch node SW away from sensitive small-
5) Connect the INTV
6) Does the V
7) For applications with multiple switching power con-
C
B
plate of C
ground at the source of the bottom MOSFET
signal nodes. Ideally the switch node should be placed
on the opposite side of the power MOSFETs from the
LTC1625.
to the INTV
capacitor carries the MOSFET gate drive current.
C
(R1, R2) must be connected between the (+) plate of
C
LTC1625 in order to keep the high impedance V
node short.
verters connected to the same V
filter capacitance for the LTC1625 is not shared with the
other converters. AC input current from another con-
verter will cause substantial input voltage ripple that
may interfere with proper operation of the LTC1625. A
few inches of PC trace or wire ( 100nH) between C
and V
+
OUT
OUT
C
4.7 F
VCC
? In adjustable applications, the resistive divider
IN
and signal ground. Place the divider near the
is sufficient to prevent sharing.
OUT
OSENSE
M1
Si4412DY
M2
Si4412DY
CC
. Connect the (–) plate of C
pin and the power ground pin. This
MBRS140T3
CC
pin connect directly to the (+) plate of
15 H
L1
D1
decoupling capacitor C
+
1625 F09
C
22 F
35V
+
IN
2
IN
C
100 F
10V
0.065
OUT
2
, ensure that the input
V
12V TO 22V
V
3.3V
2A
IN
OUT
OUT
VCC
to power
closely
OSENSE
IN