LTC1872B Datasheet, PDF (1/12 Pages) Linear Technology – Constant Frequency Current Mode Step-Up DC/DC Controller in ThinSOT

LTC1872B
Constant Frequency
Current Mode Step-Up
DC/DC Controller in ThinSOT
FEATURES
s _{Burst Mode}^TM _{Operation Disabled for Lower Output}
Ripple at Light Loads
s _{High Efficiency: Over 90%}
s _{High Output Currents Easily Achieved}
s _{Wide VIN Range: 2.5V to 9.8V}
s _{VOUT Limited Only by External Components}
s _{Constant Frequency 550kHz Operation}
s _{Current Mode Operation for Excellent Line and Load}
Transient Response
s _{Shutdown Mode Draws Only 8µA Supply Current}
s _{Low Profile (1mm) ThinSOT}^TM _Package
U
APPLICATIO S
s _{Optical Communications}
s _{Lithium-Ion-Powered Applications}
s _{Cellular Telephones}
s _{Wireless Devices}
s _{Portable Computers}
s _Scanners
DESCRIPTIO
The LTC^®1872B is a constant frequency current mode
step-up DC/DC controller providing excellent AC and DC
load and line regulation. The device incorporates an accu-
rate undervoltage lockout feature that shuts down the
LTC1872B when the input voltage falls below 2.0V.
The LTC1872B provides a ±2.5% output voltage accuracy
and consumes only 270µA of quiescent current. In shut-
down, the device draws a mere 8µA.
High constant operating frequency of 550kHz allows the
use of a small external inductor. The constant frequency
operation is maintained down to very light loads, resulting
in less low frequency noise generation over a wide load
current range.
The LTC1872B is available in a 6-lead low profile (1mm)
ThinSOT package. For a Burst Mode operation enabled
version of the LTC1872B, please refer to the LTC1872 data
sheet.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and ThinSOT are trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
147k
220pF
80.6k
1
I_TH/RUN
5
V_IN
LTC1872B
2
GND
SENSE^{– 4}
3
V_FB
6
NGATE
422k
R1
0.03Ω
L1
4.7µH
M1 ^D1
C1
10µF
10V
C2
4× 10µF
10V
V_IN
3.3V
V_OUT
5V
1A
C1: TAIYO YUDEN CERAMIC EMK325BJ106MNT
C2: MURATA GRM42-2X5R106K010AL
D1: IR10BQ015
L1: MURATA LQN6C4R7M04
M1: Si2302DS
R1: DALE 0.25W
1872B TA01
Figure 1. LTC1872B High Output Current 3.3V to 5V Boost Converter
Typical Efficiency vs Load Current*
100
V_IN = 3.3V
95 ^{VOUT = 5V}
90
85
80
75
70
65
1
10
100
LOAD CURRENT (mA)
1000
1872B TA01b
*Output ripple waveforms for the circuit of Figure 1 appear in Figure 2.
1