LTC1267_15 Datasheet, PDF (1/1 Pages) Linear Technology – Dual High Efficiency Synchronous Step-Down Switching Regulators

OBSOLETE:
FOR INFORMATION PURPOSES ONLY
Contact Linear Technology for Potential Replacement
FEATURES
I _{Dual Outputs: 3.3V and 5V, Two Adjustables or}
Adjustable and 5V
I _{Wide VIN Range: 4V to 40V}
I _{Ultra-High Efficiency: Up to 95%}
I _{Low Supply Current in Shutdown: 20µA}
I _{Current Mode Operation for Excellent Line and Load}
Transient Response
I _{High Efficiency Maintained Over a Wide Output}
Current Range
I _{Independent Micropower Shutdown}
I _{Very Low Dropout Operation: 100% Duty Cycle}
I _{Synchronous FET Switching for High Efficiency}
I _{Available in Standard 28-Pin SSOP}
APPLICATI S
I _{Notebook and Palmtop Computers}
I _{Battery-Operated Digital Devices}
I _{Portable Instruments}
I _{DC Power Distribution Systems}
LTC1267
LTC1267-ADJ/LTC1267-ADJ5
Dual High Efficiency
Synchronous Step-Down
Switching Regulators
DESCRIPTIO
The LTC^®1267 series are dual synchronous step-down
switching regulator controllers featuring automatic Burst
Mode^TM operation to maintain high efficiencies at low
output currents. The LTC1267 is composed of two sepa-
rate regulator blocks, each driving a pair of external comple-
mentary power MOSFETs at switching frequencies up to
400kHz. The LTC1267 uses a constant off-time current-
mode architecture to provide constant ripple current in the
inductor and provide excellent line and load transient
response.
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 voltage. The output current level is
user-programmable via an external current sense resistor.
The LTC1267 series is ideal for applications requiring dual
output voltages with high conversion efficiencies over a
wide load current range in a small amount of board space.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATI
V_IN
5.4V to 25V
V_OUT3
3.3V
2A
C_IN3
100µF
50V
R_SENSE3
0.05Ω
3.3µF
P-CH
Si9435DY
L3
20µH
D3
MBRS140T3
C_OUT3
220µF
10V
×2
1N4148
0.15µF
8
3
1
0.1µF
1000pF
4 ^{VCC3 CAP3 VCC}
5 ^{PGATE 3}
PDRIVE 3
14 _{SENSE+ 3}
13
12
SENSE^– 3
SHDN3
6 _{NGATE 3}
N-CH
Si9410DY
PGND3 SGND3 C_T3
7
11 9
0.15µF
2
27 26
28
1
V_IN MSHDN
LTC1267
CAP5
EXT V_CC V_{CC5 25}
PGATE 5
PDRIVE 5 ²⁴
SENSE⁺ 5 ¹⁸
SENSE^– 5 ¹⁷
19
SHDN5
NGATE 5 ²³
I_TH3 I_TH5 C_T5 SGND5 PGND5
10
15 16
20 22
C_T3
C_C3
C_C5
C_T5
270pF 3300pF 3300pF 270pF
1N4148
+
P-CH
Si9435DY
0.1µF
L5
33µH
3.3µF
R_SENSE5
0.05Ω
1000pF
N-CH
Si9410DY
D5
MBRS140T3
+
R_SENSE3: KRL SL-1R050J
L3: COILTRONICS CTX20-4
R_C3 RC5
1k
1k
R_SENSE5: KRL SL-1R050J
L5: COILTRONICS CTX33-4
+ C_IN5
100µF
50V
V_OUT5
5V
2A
C_OUT5
220µF
10V
×2
SHDN3, SHDN5, MSHDN
0V = NORMAL, >2V = SHDN
LTC1267 • F01
Figure 1. High Efficiency Dual 3.3V, 5V
1