LTC3832-1ES8#TR Linear Technology, LTC3832-1ES8#TR Datasheet - Page 10

• Manufacturer Part Number: LTC3832-1ES8#TR
• Description: IC CTRLR DC/DC SYNC BUCK 8-SOIC
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3832-1ES8#TR

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 2.5V
• Current - Output: 20A
• Frequency - Switching: 300kHz
• Voltage - Input: 3 ~ 8 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

LTC3832/LTC3832-1
APPLICATIO S I FOR ATIO
remains at a reduced voltage until the overload is re-
moved. Serious overloads generate a large overdrive at
CC, allowing it to pull SS down quickly and preventing
damage to the output components. By using the R
of Q1 to measure the output current, the current limiting
circuit eliminates an expensive discrete sense resistor that
would otherwise be required. This helps minimize the
number of components in the high current path.
The current limit threshold can be set by connecting an
external resistor R
supply at the drain of Q1. The value of R
by:
where:
The R
keep the current limit threshold constant, the internal
12 A sink current at I
temperature coefficient to provide first order correction
for the temperature coefficient of R
In order for the current limit circuit to operate properly and
to obtain a reasonably accurate current limit threshold, the
I
source pins. In addition, connect a 0.1 F decoupling
capacitor across R
wise, noise spikes or ringing at Q1’s source can cause the
actual maximum current to be greater than the desired
current limit set point. Due to switching noise and varia-
tion of R
highly accurate. The current limiting circuitry is primarily
10
IMAX
R
I
I
I
f
L
R
I
LMAX
LOAD
RIPPLE
OSC
IMAX
O
IMAX
DS(ON)Q1
and I
= Inductor value
DS(ON)
= LTC3832 oscillator frequency = 300kHz
= Internal 12 A sink current at I
= Maximum load current
= I
DS(ON)
= (I
= Inductor ripple current
FB
LOAD
of Q1 usually increases with temperature. To
pins must be Kelvin sensed at Q1’s drain and
LMAX
V
= On-resistance of Q1 at I
IN
f
, the actual current limit trip point is not
OSC
+ (I
–
)(R
IMAX
V
IMAX
U
RIPPLE
OUT
DS(ON)Q1
L
O
from the I
MAX
to filter switching noise. Other-
U
V
/2)
V
OUT
IN
is designed with a positive
)/I
IMAX
MAX
W
DS(ON)Q1
pin to the main V
IMAX
LMAX
MAX
is determined
.
U
DS(ON)
IN
Oscillator Frequency
The LTC3832 includes an onboard current controlled
oscillator that typically free-runs at 300kHz. The oscillator
frequency can be adjusted by forcing current into or out of
the FREQSET pin. With the pin floating, the oscillator runs
at about 300kHz. Every additional 1 A of current into/out
of the FREQSET pin decreases/increases the frequency by
10kHz. The pin is internally servoed to 1.265V. The
frequency can be estimated as:
where R
nected between FREQSET and the external voltage source
V
meant to prevent damage to the power supply circuitry
during fault conditions. The exact current level where the
limiting circuit begins to take effect will vary from unit to
unit as the R
as much as 40%, and with 33% variation on the
LTC3832’s I
the current limit threshold.
The R
low. This occurs during power up when PV
up. To prevent the high R
limit, the LTC3832 will disable the current limit circuit if
PV
operation of the current limit circuit, PV
least 2.5V above V
when G1 is low, allowing the use of the external charge
pump to power PV
EXT
LTC3832
CC1
f
.
DS(ON)
CC
300
is less than 2.5V above V
FSET
+
–
kHz
MAX
DS(ON)
is high if the V
is a frequency programming resistor con-
Figure 4. Current Limit Setting
current, this can give a 73% variation on
1 265
12 A
.
CC
CC1
of Q1 varies. Typically, R
R
when G1 is high. PV
.
FSET
V V
I
R
MAX
DS(ON)
I
12
13
FB
IMAX
–
GS
EXT
1k
G1
G2
from activating the current
applied to the MOSFET is
•
0.1 F
10
CC
1
kHz
. To ensure proper
V
IN
A
Q1
Q2
CC1
CC1
CC1
L
O
DS(ON)
must be at
can go low
is ramping
+
+
sn3832 3832fs
varies
3832 F04
C
C
IN
V
OUT
OUT