1
Rev. 0
DESCRIPTION
LTC3315A
3.3V V
IN
, Dual 2A, 2MHz Buck Regulators at
1.2V and 1.8V Outputs in a 74mm
2
Solution
Demonstration Circuit DC3123A features the
dual 5V, 2A Synchronous Step-Down DC/DC regulators
operating at 2MHz. One regulator provides a 1.2V output
and the other provides 1.8V, both up to a 2A load. The
LTC3315A supports adjustable output voltages from 0.5V
to V
IN
, operating frequencies from 1MHz up to 3MHz. The
LTC3315A is a compact, high efficiency, and high speed
synchronous monolithic step-down switching regulator.
Fast minimum on-time of 25ns enables high V
IN
to low
V
OUT
conversion at high frequency.
The DC3123A operating mode may be selected as Burst
Mode operation, Skip mode or Forced Continuous (FC)
mode. Setting JP1 to the FC/SYNC position will allow
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PERFORMANCE SUMMARY
the LTC3315A to sync to a clock frequency from 1MHz
to 3MHz. The LTC3315A operates in Forced Continuous
mode when syncing to an external clock.
The LTC3315A data sheet gives a complete description
of the device, operation and application information. The
data sheet must be read in conjunction with this demo.
The LTC3315A is assembled in a 1.6mm × 1.6mm WLCSP
package.
The Efficiency vs Load graph shows the efficiency and
the power loss of the circuit with a 3.3V input in Burst
Mode operation.
Design files for this circuit board are available
Specifications are at T
A
= 25°C
Efficiency vs Load Current Burst
Mode Operation
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Supply Range (V
IN
)
2.25
5.5
V
Internal Oscillator Frequency (f
SW
)
1.9
2.0
2.1
MHz
Top Switch On Time
25
ns
V
OUT1
0 to 2A
1.2
V
V
OUT2
0 to 2A
1.8
V
680nH
22µF
140k
100k
3.3pF
1µF
1µH
1M
261k
100k
1µF
22µF
3.3pF
V
IN
SW1
FB1
SW2
FB2
PGOOD
dc3123a F01
EN2
MODE/SYNC
GND
V
IN
V
IN
LTC3315A
V
IN
2.25V TO 5.5V
V
OUT1
1.2V, 2A
V
OUT2
1.8V, 2A
f
SW
= 2MHz
EN1
0.1µF
10µF
10µF
V
IN
V
IN
= 3.3V
1.2 V
OUT
1.8 V
OUT
I
OUT
(A)
0.001
0.01
0.1
1
3
70
75
80
85
90
95
EFFICIENCY (%)
dc3123a TA01b
