DEMO MANUAL DC1976A-B
LTC3676EUJ-1
Power Management Solution for
Application Processors with DDR
Description
Demonstration circuit 1976A-B is a multioutput power
supply with a pushbutton controller and I
2
C, featuring the
LTC
®
3676EUJ-1.
The LTC3676EUJ-1 has four synchro-
nous buck regulators, an always-on LDO and three LDO
regulators. The input voltage range of the LTC3676EUJ-1
is ideal for single-cell Li-Ion/Polymer battery applications.
The switching regulator settings, such as enables, feed-
back voltages, operating modes and other functions,
can be controlled via I
2
C. All of the regulators, except
the always-on LDO1 and LD04, can also be enabled via
external enable pins. After the first regulator is enabled,
the remaining enable pins use a precision threshold to
allow hardwired power-up sequences. All the regulators,
except LDO1, can also be enabled via the I
2
C.
The LTC3676EUJ-1 has three status registers, PGSTATL,
PGSTATR and IRQSTAT, that can be used to determine
the current state of the device.
The three status registers, which can be read via I
2
C,
indicate which regulators are in regulation and if a UV or
OT event occurred. The command registers, which are
used to control the switching regulators and program the
special functions, can also be read back via I
2
C to assure
the correct data was received.
The LTC3676-1 has a ±1.5A buck regulator configured to
support DDR termination plus a VTTR reference output.
Refer to the LTC3676EUJ-1 data sheet for more details on
the electrical and timing specifications and for an explan-
ation of the different device options.
Design files for this circuit board are available at
http://www.linear.com/demo
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
QuikEval is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
performance summary
SYMBOL
V
IN
V
BUCK1
V
BUCK2
V
BUCK3
V
BUCK4
V
LDO1
V
LDO2
V
LDO3
V
LDO4
PARAMETER
Input Voltage Range
Buck Regulator 1 Output Voltage
Buck Regulator 2 Output Voltage
Buck Regulator 3 Output Voltage
Buck-Boost Regulator Output Voltage
LDO1 Regulator Output Voltage
LDO2 Regulator Output Voltage
LDO3 Regulator Output Voltage
LDO4 Regulator Output Voltage
Specifications are at T
A
= 25°C
MIN
2.7
0.95 •
V
BUCK4
/2
0.76
0.76
0.82
2.92
2.73
1.75
1.16
TYP
V
BUCK4
/2
1.38
1.38
1.50
3.01
2.81
1.80
1.20
MAX
5.5
1.05 •
V
BUCK4
/2
1.58
1.58
1.71
3.10
2.89
1.85
1.24
UNITS
V
V
V
V
V
V
V
V
V
CONDITIONS
Buck 1 Enabled, I
BUCK1
= 0 ~ 1.5A
Buck 2 Enabled, I
BUCK2
= 0 ~ 1.5A
Buck 3 Enabled, I
BUCK3
= 0 ~ 2.5A
Buck4 Enabled, I
BUCK4
= 0 ~ 2.5A
LDO1 Is Always On, I
LDO1
= 0 ~ 25mA
LDO2 Enabled, I
LDO2
= 0 ~ 300mA
LDO3 Enabled, I
LDO3
= 0 ~ 300mA
LDO4 Enabled, I
LDO4
= 0 ~ 300mA
dc1976abfa
1
DEMO MANUAL DC1976A-B
Quick start proceDure
1. Ensure that JP1 to JP3, SW1 and SW2 are in their
default positions, as shown in Figure 1. Set PS1 to 5V
and turn on. The RST0 LED should light until LDO1
comes on, and the PGOOD LED should come on and
stay on
NOTE: The DV
CC
voltage level may be selected on the
DC590B. This is done by setting the V
CCIO
jumper, JP6,
on the DC590B board to one of the following settings:
3.3V, 5V, removed for 2.7V, or set to external if an external
supply is used. Please set DV
CC
to 5V.
2. Start the Linear Technology QuikEval™ program. This
program should automatically detect the presence of
the LTC3676EUJ-1 demo board (DC1976A-B) and
activate the appropriate GUI, as seen in Figure 3. The
GUI reads back the current voltages of the regulators.
LDO1 should read 3V, and V
IN
should read 5V; all others
should be 0V.
3. Press the PB1 button on the DC1976A-B for more
than 0.5s; all of the power supplies should come up
and the displayed GUI page should match Figure 3.
The sequencing for these supplies was set by Linear
Technology, using resistor divider networks from the
supply outputs to control the ENx lines.
4. Each of the supplies can be loaded to test the regulators,
but be aware that LDO2~4 are powered from V
IN
, and
the dissipation can be significant. If significant current
is desired from these regulators, care with input voltage
selection will be required.
5. Press and hold the PB1 button for more than 5s, and
all of the regulators, except LDO1, will shut down. The
GUI will show the voltages for all regulators, other than
always-on LDO1, as 0V.
6. Refer to the Using the LTC3676EUJ-1 Software section
for more information on how to control the device using
the LTC3676EUJ-1 control window.
7. Refer to the LTC3676EUJ-1 data sheet for more details
on how the LTC3676EUJ-1 operates.
8. When done, close the LTC3676EUJ-1 GUI and turn off
all loads and power supplies.
2
dc1976abfa
DEMO MANUAL DC1976A-B
Quick start proceDure
Note: All connections from equipment should be Kelvin connected directly to the board pins to
which they are connected on this diagram. Any input or output leads should be twisted-pair.
Figure 1. Proper Measurement Equipment Setup
Figure 2. Measuring Input or Output Ripple
VIN
GND
dc1976abfa
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DEMO MANUAL DC1976A-B
using the Ltc3676euJ-1 software
Introduction
The LTC3676EUJ-1 GUI provides control of most aspects
of operation of the LTC3676EUJ-1. The LTC3676EUJ-1
GUI also provides a means to manage the feedback divider
resistors, turn the regulators on and off manually, and
even to experiment with sequencing.
The LTC3676EUJ-1 GUI is composed of four forms:
n
View the LTC3676EUJ-1 Product Page
This button opens your default Internet browser, and
searches the Linear Technology Corporation website for
information on the LTC3676EUJ-1 when an Internet con-
nection is available.
Buck2 ~ Buck4 and LDO2~LDO4 Sections
These sections control most aspects of the regulator
operation. Some of the controls for the regulators are on
the Advanced Settings form. Please consult the data sheet
for operation of these bits.
Whenever the DAC sliders are changed or the regulator
is switched between normal and standby, the appropriate
control registers are changed.
If the text box has a grey background, it cannot be directly
edited. A good example of this is the command registers
SCR1, OVEN, SCR2, etc., at the bottom of the LTC3676
form. These registers are changed by the various controls
on the form.
The Auto Readback Enabled button determines if the
IRQSTAT, PGSTATL and PGSTATR values are automatically
read back. If automatic readback is disabled, the Readback
button will do a one-time readback.
The Auto Update Enabled button determines if the com-
mand registers are automatically sent to the LTC3676 on
change, and if the values of these registers are automati-
cally read back. If automatic update is disabled, the Update
All button will update all the command registers and read
back the values.
For all the automatic update modes, an internal 100ms
timer is used, so all values will be updated every 100ms,
if enabled.
The LTC3676 (DC1976A-B) form (Figure 3) is brought
up by the QuikEval program.
The Manage Resistors form (Figure 4) is brought up by
pressing the Change Resistor Divider Networks button
on the LTC3676 form.
The Advanced Settings form (Figure 5) is brought up by
pressing the Advanced Settings button on the LTC3676
form.
The Sequencing form is brought up by pressing the
Change LTC3676 Sequencing button.
n
n
n
The sequencing form, in turn, contains three tabs: Direct
(Figure 6), Table (Figure 7) and Shutdown (Figure 8).
These allow direct control and table based sequencing,
respectively, and the shutdown sequence.
SW1, positions 1 to 6, sets the source of the ENx signals
to the preselected resistor networks or to the on-board
microcontroller. SW1 should be set to Resistor Control
for normal mode, and µC Control for sequence modes
(Direct and Table).
SW2 controls the source of PWR_ON. Resistor Control,
PWR_ON = V
LDO3
, makes the source the LD03 regulator
output. PWR_ON = µC makes it controlled by the on-board
microcontroller. This switch should be set to Resistor Con-
trol for normal mode and µC Control for sequence modes.
4
dc1976abfa
DEMO MANUAL DC1976A-B
using the Ltc3676euJ-1 software
Figure 3. Main Form
Figure 4. Manage Resistors Form
dc1976abfa
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