LTC1875_15 Datasheet, PDF (1/20 Pages) Linear Technology – 1.5A Monolithic Synchronous Step-Down Regulator

LTC1875
15µA Quiescent Current
1.5A Monolithic Synchronous
Step-Down Regulator
FEATURES
s _{High Efficiency: Up to 95%}
s _{Low Quiescent Current: Only 15µA with No Load}
s _{550kHz Constant Frequency Operation}
s _{2.65V to 6V Input Voltage Range}
s _{VOUT from 0.8V to VIN, IOUT to 1.5A}
s _{True PLL Frequency Locking from 350kHz to 750kHz}
s _{Power Good Output Voltage Monitor}
s _{Low Dropout Operation: 100% Duty Cycle}
s _{Burst Mode}^® _{or Pulse Skipping Operation}
s _{Current Mode Operation for Excellent Line and Load}
Transient Response
s _{Shutdown Mode Draws < 1µA Supply Current}
s _{±2% Output Voltage Accuracy}
s _{Overcurrent and Overtemperature Protected}
s _{Available in 16-Lead SSOP Package}
U
APPLICATIO S
s _{Portable Computers}
s _{Portable Instruments}
s _{Wireless Modems}
DESCRIPTIO
The LTC^®1875 is a high efficiency 1.5A monolithic syn-
chronous buck regulator using a constant frequency,
current mode architecture. Operating supply current is
only 15µA with no load and drops to < 1µA in shutdown.
The input supply voltage range of 2.65V to 6V makes the
LTC1875 ideally suited for single Li-Ion battery-powered
applications. 100% duty cycle provides low dropout op-
eration, extending battery life in portable systems.
The switching frequency is internally set to 550kHz, allow-
ing the use of small surface mount inductors and capaci-
tors. For noise sensitive applications, the LTC1875 can be
externally synchronized from 350kHz to 750kHz. Burst
Mode operation is inhibited during synchronization or
when the SYNC/MODE pin is pulled low.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Low
output voltages are easily supported with a 0.8V feedback
reference voltage. The LTC1875 is available in a 16-lead
SSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
High Efficiency Step-Down Converter
V_IN
2.65V TO 6V _CIN
22µF
150k
47pF
220pF
SV_IN
RUN/SS
PV_IN
SYNC/MODE SWP
LTC1875
PGOOD
SWN
I_TH
PGND
V_FB
SGND
L1
6.8µH
88.7k
28.0k
V_OUT*
3.3V
+
C_OUT
47µF
1875 TA01
C_IN: TAIYO YUDEN CERAMIC JMK325BJ226MM
C_OUT: SANYO POSCAP 6TPA47M
L1: TOKO 646CY-6R8M
*V_OUT CONNECTED TO V_IN (MINUS SWITCH AND L1 VOLTAGE DROP) FOR 2.65V < V_IN < 3.3V
Efficiency vs Output Load Current
100
95
V_IN = 3.6V
90
85
V_IN = 4.2V
80
V_IN = 6V
75
70
65
60
55
0.1
Burst Mode OPERATION
V_OUT = 3.3V
L = 6.8µH
1
10
100
OUPUT CURRENT (mA)
1000
1875 TA01a
1875f
1