LINEAR Dual Output Monolithic Synchronous Buck Regulator - Design Note 1020 Tom Gross User Manual
Summary
A high-efficiency, dual-output synchronous buck regulator designed for stable power delivery in advanced distributed systems. This component powers crucial rails (e.g., 1.8V and 3.3V) from 3.6V to 15V input while supporting up to 3A per channel. The manual thoroughly details deployment strategies, including two-phase out-of-phase operation that significantly minimizes input current ripple and EMI noise. It is essential for engineers creating high-performance electronic systems demanding precise load regulation and transient response.
Page 1 Text Content
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Dual Output Monolithic Synchronous Buck Regulator Operates from 3.6V to 15V Inputs and Delivers 3A Per Channel – Design Note 1020 Tom Gross Introduction The LTC3633 is a high efficiency, dual output monolithic VOUT = 3.3V synchronous step-down switching regulator, capable of delivering 3A of output current per channel from input voltages between 3.6V and 15V. Its compact 4mm × 5mm VOUT = 1.8V QFN package has very low thermal impedance eliminating the need for an external heat sink. Its high input voltage
VIN = 12V
capability makes the LTC3633 ideal for 12V distributed
FSW = 2MHz
power systems. Burst Mode® OPERATION
0.5 1.5 2.5 3.5 1.8V and 3.3V 2MHz Buck Regulator LOAD CURRENT (A)
EF DN1020 F02 FI CI EN CY
Figure 1 shows a LTC3633 12VIN to 1.8VOUT and 3.3VOUT,
Figure 2. High Efficiency from Each Channel for the
3A, buck regulator. With the frequency setting pin, RT,
Circuit in Figure 1
connected to the internal 3.3V regulator rail (INTVCC), this
circuit runs at 2MHz —the LTC3633 switching frequency By connecting the phase mode pin (PHMODE) to is programmable from 500k Hz to as high as 4MHz, and INTVCC, the two internal regulators operate 180 degrees can also be synchronized to an external clock—reducing out-of-phase with respect to each other, reducing the the value and size of the output capacitors and inductor. input current ripple, and thus, the number and value of Even with this high switching frequency, the efficiency of input capacitors. Due to a controlled on-time design, this circuit is good: 87% at full load for the 3.3V regula- the LTC3633 achieves very fast load transient response
tor and 82% at full load for the 1.8V regulator, at 12VIN L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of
(see Figure 2).
their respective owners.
VIN 3.6V TO 15V
CIN3 CIN2 CIN1 22µF 47µF 47µF 16V 16V 16V
POWER SIGNAL GROUND GROUND
VIN1 VIN1 RUN1 RUN2 VIN2 VIN2
L1 BOOST1 BOOST2 L2
CBST1 CBST2
VOUT1 1µH 1µH VOUT214
SW1 SW2
COUT1 VISHAY VISHAY
COUT2
22µF IHLP-2020BZER1R0M01 IHLP-2020BZER1R0M01 R4
SW1 SW2 22µF
20k VON1 VON2LTC3633EUFD
1% CFFW2
TRACKSS2 VFB2 10p F
COUT3
CFFW1 COUT4
10p F VFB1 PGND 22µF
TRACKSS1 SGND 13.7k
10k ITH1 RT INTVCCPHMODE MODE/SYNC V2P5 ITH2 PGOOD2PGOOD1
COUT5
1% COUT6
RPG1 RPG2
PGOOD1 PGOOD2VOUT1 VOUT2
1.8V 3.3V 3A 3A DN1020 F01
Figure 1. LTC3633: 1.8VOUT and 3.3VOUT, 2MHz Buck Regulator
Page Summary Contents For LINEAR Dual Output Monolithic Synchronous Buck Regulator - Design Note 1020 Tom Gross User Manual
Manual Details
| Brand | Linear |
|---|---|
| Pages | 2 |
| File Size | 529.70 KB |
| Published | June 17, 2026 |
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Frequently Asked Questions
What is the effective input voltage range for this regulator?
It operates from input voltages between 3.6V and 15V.
How efficient is the LTC3633 at full load?
The efficiency achieves 87% at full load for the 3.3V regulator and 82% at full load for the 1.8V regulator.
Does the device require a large external heat sink?
No, its compact package has very low thermal impedance, eliminating the need for an external heat sink.
What operational modes are available for the switching frequency (RT)?
The operating frequency can be programmable from 500kHz to as high as 4MHz, and also synchronized to an external clock.