鈮?/div>
V
IN
No Schottky Diode Required
1.19V
鹵
1% Reference Output Pin
Selectable Burst Mode
TM
Operation/Pulse
Skipping Mode
Low Dropout Operation: 100% Duty Cycle
Precision 2.7V Undervoltage Lockout
Current Mode Control for Excellent Line and
Load Transient Response
Low Quiescent Current: 200碌A(chǔ)
Shutdown Mode Draws Only 15碌A(chǔ) Supply Current
Available in 8-Lead SO Package
The LTC
廬
1707 is a high efficiency monolithic current
mode synchronous buck regulator using a fixed frequency
architecture. The operating supply range is from 8.5V
down to 2.85V, making it suitable for both single and dual
lithium-ion battery-powered applications. Burst Mode op-
eration provides high efficiency at low load currents.
100% duty cycle provides low dropout operation, extend-
ing operating time in battery-powered systems.
The switching frequency is internally set at 350kHz,
allowing the use of small surface mount inductors. For
noise sensitive applications it can be externally synchro-
nized up to 550kHz. Burst Mode operation is inhibited
during synchronization or when the SYNC/MODE pin is
pulled low preventing low frequency ripple from interfer-
ing with audio circuitry. Soft-start is provided by an
external capacitor.
The internal synchronous MOSFET switch increases effi-
ciency and eliminates the need for an external Schottky
diode, saving components and board space. Low output
voltages down to 0.8V are easily achieved due to the 0.8V
internal reference. The LTC1707 comes in an 8-lead SO
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
s
s
Cellular Telephones
Portable Instruments
Wireless Modems
RF Communications
Distributed Power Systems
Single and Dual Cell Lithium
TYPICAL APPLICATIO
V
IN
*
3V TO
8.5V
6
V
IN
RUN
SW
V
REF
V
FB
5
8
3
100
V
OUT
= 3.3V
95
V
IN
= 6V
V
IN
= 3.6V
15碌H
+
22碌F
16V
2
+
249k
100碌F
6.3V
V
OUT
3.3V
EFFICIENCY (%)
90
85
80
75
V
IN
= 8.4V
LTC1707
7
SYNC/MODE
1
47pF
I
TH
80.6k
GND
4
*V
OUT
FOLLOWS V
IN
FOR
3V < VIN < 3.3V
1707 F01a
70
1
10
100
OUTPUT CURRENT (mA)
1000
1707 F01b
Figure 1a. High Efficiency Low Dropout Step-Down Converter
Figure 1b. Efficiency vs Output Load Current
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
U
U
1