LTC3801B_15 Datasheet, PDF (1/12 Pages) Linear Technology – Micropower Constant Frequency Step-Down DC/DC Controllers in ThinSOT

LTC3801/LTC3801B
Micropower
Constant Frequency Step-Down
DC/DC Controllers in ThinSOT
FEATURES
s _{High Efficiency: Up to 94%}
s _{Very Low No-Load Quiescent Current:}
Only 16µA (LTC3801)
s _{High Output Currents Easily Achieved}
s _{Internal Soft-Start}
s _{Wide VIN Range: 2.4V to 9.8V}
s _{Low Dropout: 100% Duty Cycle}
s _{Constant Frequency 550kHz Operation}
s _{Burst Mode}^® _{Operation for High Efficiency}
at Light Loads (LTC3801)
s _{Burst Mode Operation Disabled for Lower Output}
Ripple at Light Loads (LTC3801B)
s _{Output Voltage as Low as 0.8V}
s _{±1.5% Voltage Reference Accuracy}
s _{Current Mode Operation for Excellent Line and Load}
Transient Response
s _{Only 6µA Supply Current in Shutdown (LTC3801)}
s _{Low Profile (1mm) SOT-23 Package}
U
APPLICATIO S
s _{1- or 2-Cell Li-Ion Battery-Powered Applications}
s _{Wireless Devices}
s _{Portable Computers}
s _{Distributed Power Systems}
DESCRIPTIO
The LTC^®3801/LTC3801B are constant frequency cur-
rent mode step-down DC/DC controllers in a low profile
(1mm max) 6-lead SOT-23 (ThinSOT^TM) package. The
parts provide excellent AC and DC load and line regula-
tion with ±1.5% output voltage accuracy. The LTC3801
consumes only 195µA of quiescent current in normal
operation, dropping to 16µA under no-load conditions.
The LTC3801/LTC3801B incorporate an undervoltage lock-
out feature that shuts down the device when the input
voltage falls below 2.2V. The LTC3801 automatically
switches into Burst Mode operation at light loads which
enhances efficiency at low output current. In the LTC3801B,
Burst Mode operation is disabled for lower output ripple at
light loads.
To further maximize the life of a battery source, the
external P-channel MOSFET is turned on continuously in
dropout (100% duty cycle). High switching frequency of
550kHz allows the use of a small inductor.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
550kHz Micropower Step-Down DC/DC Controller
220pF
10k
402k
I_TH/RUN V_IN
LTC3801/
LTC3801B
GND SENSE^–
V_FB
PGATE
866k
0.025Ω
V_IN
2.7V TO 9.8V
10µF
4.7µH
+
47µF
V_OUT
2.5V
2A
3801 TA01
LTC3801 Efficiency vs Load Current*
100
V_OUT = 2.5V
95
V_IN = 4.2V
90
V_IN = 3.3V
85
V_IN = 6.6V
80
75
70
V_IN = 9.8V V_IN = 8.4V
65
60
55
50
0.1
1
10
100 1000 10000
LOAD CURRENT (mA)
3801 TA02
*SEE NO-LOAD I_Q vs INPUT VOLTAGE ON THE LAST PAGE OF THIS DATA SHEET
sn3801 3801fs
1