LTC1159 Datasheet, PDF (1/20 Pages) Linear Technology – High Efficiency Synchronous Step-Down Switching Regulators

LTC1159/LTC1159-3.3/LTC1159-5
High Efficiency Synchronous
Step-Down Switching Regulators
FEATURES
s _{Operation from 4V to 40V Input Voltage}
s _{Ultra-High Efficiency: Up to 95%}
s _{20µA Supply Current in Shutdown}
s _{High Efficiency Maintained Over Wide Current Range}
s _{Current Mode Operation for Excellent Line and Load}
Transient Response
s _{Very Low Dropout Operation: 100% Duty Cycle}
s _{Short-Circuit Protection}
s _{Synchronous FET Switching for High Efficiency}
s _{Adaptive Non-Overlap Gate Drives}
s _{Available in SSOP and SO Packages}
APPLICATI S
s _{Step-Down and Inverting Regulators}
s _{Notebook and Palmtop Computers}
s _{Portable Instruments}
s _{Battery-Operated Digital Devices}
s _{Industrial Power Distribution}
s _{Avionics Systems}
s _{Telecom Power Supplies}
DESCRIPTIO
The LTC^®1159 series is a family of synchronous step-down
switching regulator controllers featuring automatic Burst
Mode^TM operation to maintain high efficiencies at low
output currents. These devices drive external complemen-
tary power MOSFETs at switching frequencies up to 250kHz
using a constant off-time current-mode architecture.
A separate pin and on-board switch allow the MOSFET
driver power to be derived from the regulated output
voltage providing significant efficiency improvement when
operating at high input voltages. The constant off-time
current-mode architecture maintains constant ripple cur-
rent in the inductor and provides excellent line and load
transient response. The output current level is user pro-
grammable via an external current sense resistor.
The LTC1159 automatically switches to power saving
Burst Mode operation when load current drops below
approximately 15% of maximum current. Standby current
is only 300µA while still regulating the output and shut-
down current is a low 20µA.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATI
+
3.3µF
0.15µF
V_IN
CAP
P-GATE
V_CC
V_CC
P-DRIVE
EXTV_CC
LTC1159-5
0V = NORMAL
>2V = SHUTDOWN
3300pF
1k
C_T
300pF
SHDN1
SHDN2
I_TH
C_T
S-GND
SENSE ⁺
SENSE ^–
N-GATE
P-GND
V_IN
1N4148
0.1µF
Si9435DY
+ CIN
100µF
100V
D1
MBRS140T3
L*
33µH
0.01µF
Si9410DY
R_SENSE
0.05Ω
V_OUT
5V/2A
+ _COUT
220µF
LTC1159 • F01
*COILTRONICS CTX33-4-MP
Figure 1. High Efficiency Step-Down Regulator
LTC1159-5 Efficiency
100
FIGURE 1 CIRCUIT
V_IN = 10V
90
V_IN = 20V
80
70
60
0.02
0.2
LOAD CURRENT (A)
2
LTC1159 • TA01
1