LTC1622 Datasheet, PDF (1/16 Pages) Linear Technology – Low Input Voltage Current Mode Step-Down DC/DC Controller

FEATURES
s _{High Efficiency}
s _{Constant Frequency 550kHz Operation}
s _{VIN Range: 2V to 10V}
s _{Multiampere Output Currents}
s _OPTI-LOOP^TM _{Compensation Minimizes COUT}
s _{Selectable, Burst Mode Operation}
s _{Low Dropout Operation: 100% Duty Cycle}
s _{Synchronizable up to 750kHz}
s _{Current Mode Operation for Excellent Line and Load}
Transient Response
s _{Low Quiescent Current: 350µA}
s _{Shutdown Mode Draws Only 15µA Supply Current}
s _{±1.9% Reference Accuracy}
s _{Available in 8-Lead MSOP}
U
APPLICATIO S
s _{1- or 2-Cell Li-Ion Powered Applications}
s _{Cellular Telephones}
s _{Wireless Modems}
s _{Portable Computers}
s _{Distributed 3.3V, 2.5V or 1.8V Power Systems}
s _Scanners
s _{Battery-Powered Equipment}
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode and OPTI-LOOP are a trademarks of Linear Technology Corporation.
LTC1622
Low Input Voltage
Current Mode Step-Down
DC/DC Controller
DESCRIPTIO
The LTC^®1622 is a constant frequency current mode step-
down DC/DC controller providing excellent AC and DC load
and line regulation. The device incorporates an accurate
undervoltage feature that shuts the LTC1622 down when
the input voltage falls below 2V.
The LTC1622 boasts a ±1.9% output voltage accuracy and
consumes only 350µA of quiescent current. For applica-
tions where efficiency is a prime consideration and the
load current varies from light to heavy, the LTC1622 can
be configured for Burst Mode^TM operation. Burst Mode
operation enhances low current efficiency and extends
battery run time. Burst Mode operation is inhibited during
synchronization or when the SYNC/MODE pin is pulled low
to reduce noise and possible RF interference.
High constant operating frequency of 550kHz allows the
use of a small inductor. The device can also be synchro-
nized up to 750kHz for special applications. The high
frequency operation and the available 8-lead MSOP pack-
age create a high performance solution in an extremely
small amount of PCB area.
To further maximize the life of the battery source, the
P-channel MOSFET is turned on continuously in dropout
(100% duty cycle). In shutdown, the device draws a mere
15µA.
TYPICAL APPLICATIO
V_IN
2.5V TO 8.5V
R1
10k
C3
220pF
8
2
I_TH
V_IN
SENSE^–
1
7
PDRV
LTC1622
5
SYNC/MODE
470pF
4
RUN/SS
V_FB
3
6
GND
R2
0.03Ω
Si3443DV _L1
4.7µH
D1
IR10BQ015
C1
10µF
10V
R3
159k ₊
R4
75k
V_OUT
2.5V
1.5A
C2
47µF
6V
C1: TAIYO YUDEN CERAMIC EMK325BJ106MNT L1: MURATA LQN6C-4R7
C2: SANYO POSCAP 6TPA47M
R2: DALE WSL-1206 0-03Ω
D1: INTERNATIONAL RECTIFIER IR10BQ015
1622 F01a
Figure 1. High Efficiency Step-Down Converter
Efficiency vs Load Current with
Burst Mode Operation Enabled
100
V_IN = 4.2V
90 _{VIN = 3.3V}
80
V_IN = 6V
70
V_IN = 8.4V
60
50
40
1
V_OUT = 2.5V
R_SENSE = 0.03Ω
10
100
1000
LOAD CURRENT (mA)
5000
1622 F01b
1