LTC1433IGN Linear Technology, LTC1433IGN Datasheet - Page 13

• Manufacturer Part Number: LTC1433IGN
• Description: IC DC/DC CONV STEP-DOWN 16-SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC1433IGN

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3.3V, 5V, Adj
• Current - Output: 450mA
• Frequency - Switching: 125kHz ~ 240kHz
• Voltage - Input: 3 ~ 13.5 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
further reducing the current to 15 A. The low side of the
resistive divider should connect to SGND.
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1433/LTC1434. These items are also illustrated graphi-
cally in the layout diagram of Figure 13. Check the follow-
ing in your layout:
1. Are the signal and power grounds segregated? The
2. Does the LTC1433/LTC1434 V
3. Does the (+) plate of C
LTC1433/LTC1434 signal ground pin must return to
the (–) plate of C
anode of the Schottky diode and the (–) plate of C
which should have as short lead lengths as possible.
(+) plate of C
tive divider R1/R2 must be connected between the (+)
plate of C
close as possible? This capacitor provides the AC
current to the internal P-channel MOSFETs and their
drivers.
OUT
OUT
and signal ground.
? In adjustable applications, the resis-
U
OUT
. The power ground returns to the
V
C
INFORMATION
OUT
OUT
IN
U
WITH ADJUSTABLE VERSION
OUTPUT DIVIDER REQUIRED
connect to the power V
+
ONLY. CONNECT V
BOLD LINES INDICATE HIGH CURRENT PATHS
Figure 13. LTC1434 Layout Diagram (See Board Layout Check List)
TO V
OUTPUT VOLTAGE
OSENSE
OUT
W
FOR FIXED
pin connect to the
OSENSE
L1
U
C
SS
IN
10
IN
as
1
2
3
4
5
6
7
8
9
D1
,
NC
SSW
NC
BSW
SGND
NC
RUN/SS
NC
LBO
LBI
LTC1434
4. Is the Schottky diode closely connected between the
5. Keep the switching nodes, SSW and BSW away from
Design Example
As a design example, assume V
400mA and f
can start choosing all of the important components.
With no frequency synchronization required, the LTC1433
can be used for this circuit. From Figure 2, the V
0V curve is used to determine the value of the oscillator
capacitor. From the graph a value of 50pF will provide the
desired frequency.
Next the inductor value is selected. From the Maximum
Output Current vs Input Supply graph in the Typical
Performance Characteristics section, a value of L = 22 H
would be able to meet the requirement for the output load
current.
For the catch diode, a MBRS130LT3 is selected.
power ground and switch pin?
sensitive small-signal nodes V
C
V
PWRV
PLL LPF
OSENSE
OSC
0.1 F
V
PGND
PLLIN
C
PROG
SV
POR
OSC
I
TH
IN
IN
, I
TH
20
19
18
17
16
15
14
13
12
11
C
IN
and LBI.
OSC
= 200kHz. With these requirements we
C
OSC
1433/34 F13
LTC1433/LTC1434
IN
OSENSE
= 6V, V
, PLLIN, PLL LPF,
OUT
= 5V, I
PLL LPF
13
MAX
=
=