DEMO MANUAL DC1856B-B
LTM4649EY
High Efficiency 10A
Step-Down µModule Regulator
Description
Demonstration circuit 1856B-B features the
LTM
®
4649EY
µModule
®
regulator, a high performance high efficiency
step-down regulator. The LTM4649EY has an operating
input voltage range of 4.5V to 16V and is able to provide
an output current of up to 10A. The output voltage is pro-
grammable from 0.6V to 3.3V and can be remotely sensed
with the internal differential remote sensing amplifier. The
LTM4649EY is a complete DC-DC point of load regulator
in a thermally enhanced 15mm × 9mm × 4.92mm BGA
package requiring only a few input and output capacitors.
Output voltage tracking is available through the TRACK/SS
pin for supply rail sequencing. External clock synchroniza-
tion is also available through the CLKIN pin. The LTM4649
data sheet must be read in conjunction with this demo
manual for working on or modifying demo circuit 1856B-B.
Design files for this circuit board are available at
http://www.linear.com/demo/DC1856B-B
L,
LT, LTC, LTM, Linear Technology, µModule, Burst Mode and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
performance summary
PARAMETER
Input Voltage Range
Output Voltage V
OUT
Maximum Continuous Output Current
Default Operating Frequency
External Clock Sync. Frequency Range
Efficiency
Specifications are at T
A
= 25°C
VALUE
4.5V TO 16V
1V
DC
, 1.2V
DC
, 1.5V
DC
, 1.8V
DC
,
2.5V
DC
, 3.3V
DC
10A
DC
450kHz
250kHz TO 800kHz
CONDITIONS
Jumper Selectable
Derating is Necessary for Certain Operating Conditions.
See Data Sheet for Details
V
IN
= 12V, V
OUT
= 1.8V, I
OUT
= 10A
89% See Figure 2
BoarD photo
dc1856bbf
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DEMO MANUAL DC1856B-B
Quick start proceDure
Demonstration circuit 1856B-B is an easy way to evaluate
the performance of the LTM4649EY. Please refer to Figure 1
for test setup connections and follow the procedure below.
1. With power off, place the jumpers in the following posi-
tions for a typical 1.8V
OUT
application:
JP8
TRACK/SS
SS
JP7
RUN
ON
JP9
MODE
CCM
JP2
V
OUT
Select
1.8V
5. Once the proper output voltage is established, adjust
the load current within the 0A to 10A range and observe
the load regulation, efficiency, and other parameters.
Output voltage ripple should be measured at J6 with a
BNC cable and oscilloscope.
6. To observe increased light load efficiency place the
mode pin jumper (JP9) in the Burst Mode
®
operation
position. To observe increased light load efficiency with
a reduced output ripple as compared to Burst Mode
operation, place the mode pin jumper in the pulse-
skipping position.
7. For optional load transient testing apply an adjustable
positive pulse signal between IOSTEP CLK and GND
pins. The pulse amplitude sets the load step current
amplitude. The pulse width should be short (< 1ms)
and pulse duty cycle should be low (< 15%) to limit the
thermal stress on the load transient circuit. The load
step current can be monitored with a BNC connected
to J5 (10mV/A).
2. Before connecting input supply, load and meters, preset
the input voltage supply to be between 4.5V to 16V.
Preset the load current to 0A.
3. With power off, connect the load, input voltage supply
and meters as shown in Figure 1.
4. Turn on input power supply. The output voltage meter
should display the selected output voltage ± 2%.
dc1856bbf
2
DEMO MANUAL DC1856B-B
Quick start proceDure
+
+
–
A
V
–
–
LOAD
+
0A TO 10A
–
V
V
IN
–
A
+
Figure 1. Test Setup of DC1856B-B
–
+
+
dc1856bbf
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DEMO MANUAL DC1856B-B
Quick start proceDure
5V
IN
CCM Efficiency vs Load Current
100
95
EFFICIENCY %
90
85
80
75
V
OUT
= 3.3V AT 450kHZ
V
OUT
= 2.5V AT 450kHZ
V
OUT
= 1.8V AT 450kHZ
V
OUT
= 1.5V AT 450kHZ
V
OUT
= 1.2V AT 450kHZ
V
OUT
= 1V AT 450kHZ
0
1
2
3
4
6
7
5
LOAD CURRENT (A)
8
9
10
DC1856bb F02a
12V
IN
CCM Efficiency vs Load Current
95
90
EFFICIENCY %
85
80
75
70
V
OUT
= 3.3V AT 750kHZ
V
OUT
= 2.5V AT 750kHZ
V
OUT
= 1.8V AT 450kHZ
V
OUT
= 1.5V AT 450kHZ
V
OUT
= 1.2V AT 450kHZ
V
OUT
= 1V AT 450kHZ
0
1
2
3
4
6
7
5
LOAD CURRENT (A)
8
9
10
DC1856bb F02b
Figure 2. Measured Supply Efficiency at 5V
IN
and 12V
IN
dc1856bbf
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DEMO MANUAL DC1856B-B
Quick start proceDure
I
OUT STEP
: 5A/DIV
V
OUTP
: 100mV/DIV
DC1856bb F03
V
IN
(V)
12
V
OUT
(V)
1.5
C
OUT
CERAMIC
2 × 220µF/4V
Ceramic
Figure 3. Measured Load Transient Response
(5A to 10A Load Step)
V
IN
(V)
1.2
V
OUT
(V) I
OUT
(A)
1.5
10
AIRFLOW
Natural Convection
AMBIENT (°C)
29.7
Figure 4. Measured Thermal Capture
dc1856bbf
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