LT3501_15 Datasheet, PDF (1/30 Pages) Linear Technology – Monolithic Dual Tracking 3A Step-Down Switching Regulator

Features
n _{Wide Input Range: 3.1V to 25V}
n _{Two Switching Regulators with 3A Output Capability}
n _{Independent Supply to Each Regulator}
n _{Adjustable/Synchronizable Fixed Frequency}
Operation from 250kHz to 1.5MHz
n _{Antiphase Switching}
n _{Outputs Can be Paralleled}
n _{Independent, Sequential, Ratiometric or Absolute}
Tracking Between Outputs
n _{Independent Soft-Start and Power Good Pins}
n _{Enhanced Short-Circuit Protection}
n _{Low Dropout: 95% Maximum Duty Cycle}
n _{Low Shutdown Current: <10µA}
n _{20-Lead TSSOP Package with Exposed Leadframe}
Applications
n _{DSP Power Supplies}
n _{Disc Drives}
n _{DSL/Cable Modems}
n _{Wall Transformer Regulation}
n _{Distributed Power Regulation}
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LT3501
Monolithic Dual Tracking
3A Step-Down Switching
Regulator
Description
The LT^®3501 is a dual-current mode PWM step-down
DC/DC converter with two internal 3.5A switches. Inde-
pendent input voltage, feedback, soft-start and power
good pins for each channel simplify complex power
supply tracking/sequencing requirements.
Both converters are synchronized to either a common
external clock input or a resistor programmable fixed
250kHz to 1.5MHz internal oscillator. At all frequencies, a
180° phase relationship between channels is maintained,
reducing voltage ripple and component size. Programmable
frequency allows for optimization between efficiency and
external component size.
Minimum input-to-output voltage ratios are improved
by allowing the switch to stay on through multiple clock
cycles, only switching off when the boost capacitor needs
recharging, resulting in ~95% maximum duty cycle.
Each output can be independently disabled using its own
soft-start pin, or by using the SHDN pin the entire part can
be placed in a low quiescent current shutdown mode.
The LT3501 is available in a 20-lead TSSOP package with
exposed leadframe for low thermal resistance.
Typical Application
V_IN, 12V
3.3V and 1.8V Dual 3A Step-Down Converter with Output Tracking
4.7µF
4.7µH
V_IN1
SHDN
BST1
0.47µF
SW1
V_IN2
R_T/SYNC
61.9k
BST2
0.47µF
SW2
3.3µH
PMEG4005
PMEG4005
B360A
LT3501
V_OUT1
3.3V, 3A
47µF
24.9k
8.06k
470pF
10pF 40.2k
IND1
V_OUT1
IND2
V_OUT2
PG1
PG2
FB1
FB2
V_C1
V_C2
SS/TRACK1 SS/TRACK2
GND
0.1µF
B360A
10k
V_OUT2
1.8V, 3A
100µF
470pF
40.2k
8.06k
47pF
3501 TA01a
100
90
80
70
60
50
40
30
20
10
0
0
Efficiency
V_OUT1 = 5V
V_OUT1 = 3.3V
V_OUT1 = 1.8V _{VOUT1 = 2.5V}
V_IN = 12V
I_OUT2 = 0A
FREQUENCY = 500kHz
0.5 1 1.5 2
LOAD CURRENT (A)
2.5 3
3501 TA01b
3501fd
1