LTC3830ES#TRPBF Linear Technology, LTC3830ES#TRPBF Datasheet - Page 10

• Manufacturer Part Number: LTC3830ES#TRPBF
• Description: IC DC/DC CONTRLR STEP-DWN 16SOIC
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3830ES#TRPBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 3.3V, Adj
• Current - Output: 20A
• Frequency - Switching: 200kHz
• Voltage - Input: 3 ~ 8 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -

LTC3830/LTC3830-1
APPLICATIO S I FOR ATIO
The R
keep the current limit threshold constant, the internal
12µA 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 0.1µF decoupling
capacitor across R
wise, noise spikes or ringing at Q1’s source can cause the
actual current limit to be greater than the desired current
limit set point. Due to switching noise and variation of
R
accurate. The current limiting circuitry is primarily 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
±40% and with ±25% variation on the LTC3830’s I
current, this can give a ±65% variation on the current limit
threshold.
The R
low. This occurs during power up, when PV
up. To prevent the high R
limit, the LTC3830 disables the current limit circuit if
PV
10
IMAX
LTC3830
DS(ON)
DS(ON)
CC1
and I
DS(ON)
DS(ON)
CC
is less than 2.5V above V
, the actual current limit trip point is not highly
of Q1 varies. Typically, R
+
–
FB
of Q1 usually increases with temperature. To
pins must be Kelvin sensed at Q1’s drain and
is high if the V
Figure 4. Current Limit Setting
12µA
IMAX
U
I
R
MAX
MAX
I
12
13
FB
IMAX
DS(ON)
to filter switching noise. Other-
U
GS
is designed with a positive
1k
G1
G2
from activating the current
applied to the MOSFET is
DS(ON)
0.1µF
CC
W
DS(ON)Q1
V
. To ensure proper
IN
Q1
Q2
varies as much as
L
CC1
O
.
is ramping
U
+
+
3830 F04
C
C
IN
OUT
V
MAX
OUT
operation of the current limit circuit, PV
least 2.5V above V
when G1 is low, allowing the use of an external charge
pump to power PV
Oscillator Frequency
The LTC3830 includes an onboard current controlled
oscillator that typically free-runs at 200kHz. 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 200kHz. Every additional 1µA of current into/out
of the FREQSET pin decreases/increases the frequency by
10kHz. The pin is internally servoed to 1.265V, connecting
a 50k resistor from FREQSET to ground forces 25µA out
of the pin, causing the internal oscillator to run at approxi-
mately 450kHz. Forcing an external 10µA current into
FREQSET cuts the internal frequency to 100kHz. An inter-
nal clamp prevents the oscillator from running slower than
about 50kHz. Tying FREQSET to V
at this minimum speed. The LTC3830-1 and the 8-lead
LTC3830 do not have this frequency adjustment function.
Shutdown
The LTC3830 includes a low power shutdown mode,
controlled by the logic at the SHDN pin. A high at SHDN
allows the part to operate normally. A low level at SHDN for
more than 100µs forces the LTC3830 into shutdown
mode. In this mode, all internal switching stops, the COMP
and SS pins pull to ground and Q1 and Q2 turn off. The
LTC3830 supply current drops to <10µA, although off-
state leakage in the external MOSFETs may cause the total
V
temperatures. If SHDN returns high, the LTC3830 reruns
a soft-start cycle and resumes normal operation. The
LTC3830-1 does not have this shutdown function.
IN
current to be some what higher, especially at elevated
CC
CC1
when G1 is high. PV
.
CC
forces the chip to run
CC1
CC1
must be at
can go low
3830fa