LTC3619B_15 Datasheet, PDF (1/20 Pages) Linear Technology – 400mA/800mA Synchronous Step-Down DC/DC with Average Input Current Limit

LTC3619B
400mA/800mA Synchronous
Step-Down DC/DC with
Average Input Current Limit
Features
Description
n _{Programmable Average Input Current Limit:}
±5% Accuracy
n _{Dual Step-Down Outputs: Up to 96% Efficiency}
n _{Low Noise Pulse-Skipping Operation at Light Loads}
n _{Input Voltage Range: 2.5V to 5.5V}
n _{Output Voltage Range: 0.6V to 5V}
n _{2.25MHz Constant-Frequency Operation}
n _{Power Good Output Voltage Monitor for Each Channel}
n _{Low Dropout Operation: 100% Duty Cycle}
n _{Independent Internal Soft-Start for Each Channel}
n _{Current Mode Operation for Excellent Line and Load}
Transient Response
n _{±2% Output Voltage Accuracy}
n _{Short-Circuit Protected}
n _{Shutdown Current ≤ 1μA}
n _{Available in Small Thermally Enhanced 10-Lead MS}
and 3mm × 3mm DFN Packages
Applications
n _{High Peak Load Current Applications}
n _{USB Powered Devices}
n _{Supercapacitor Charging}
n _{Radio Transmitters and Other Handheld Devices}
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 5481178, 6127815,
6304066, 6498466, 6580258, 6611131.
The LTC^®3619B is a dual monolithic synchronous buck
regulator using a constant frequency current mode ar-
chitecture.
The input supply voltage range is 2.5V to 5.5V, making it
ideal for Li-Ion and USB powered applications. 100% duty
cycle capability provides low dropout operation, extend-
ing the run time in battery-operated systems. Low output
voltages are supported with the 0.6V feedback reference
voltage. Channel 1 and channel 2 can supply 400mA and
800mA output current, respectively.
The LTC3619B’s programmable average input current limit
is ideal for USB applications and for point-of-load power
supplies because the LTC3619B’s limited input current
will still allow its output to deliver high peak load currents
without collapsing the input supply. When the sum of
both channels’ currents exceeds the input current limit,
channel 2 is current limited while channel 1 remains regu-
lated. The operating frequency is internally set at 2.25MHz
allowing the use of small surface mount inductors. Internal
soft-start reduces in-rush current during start-up. The
LTC3619B is available in small MSOP and 3mm × 3mm
DFN packages. The LTC3619B is also available in a low
quiescent current, high efficiency Burst Mode^® version,
LTC3619.
Typical Application
Dual Monolithic Buck Regulator in 10-Lead 3mm × 3mm DFN
V_IN
3.4V TO 5.5V
10µF
RUN2 V_IN RUN1
PGOOD2 PGOOD1
V_OUT2
3.4V AT
800mA
1.5µH
LTC3619B
SW2
SW1
3.3µH
22pF
1190k
+
2.2mF
×2
V_FB2
V_FB1
255k
RLIM GND
SuperCap
255k ^511k
1000pF
116k
I_LIM = 475mA
V_OUT1
1.8V AT
400mA
10µF
3619B TA01
GSM Pulse Load
V_OUT
200mV/DIV
V_IN
AC-COUPLED
1V/DIV
I_OUT
500mA/DIV
I_IN
500mA/DIV
1ms/DIV
3619B TA01b
V_IN = 5V, 500mA COMPLIANT
I_LOAD = 0A to 2.2A, CHANNEL 1 UNLOADED
3619bfb
1