MSS1048-152NL AD [Analog Devices], MSS1048-152NL Datasheet - Page 18

• Manufacturer Part Number: MSS1048-152NL
• Description: Dual 5 A, 20 V Synchronous Step-Down
• Manufacturer: AD [Analog Devices]

If the overcurrent counter reaches 10, or if the FBx pin voltage
falls to 0.2 V after the soft start, the device enters hiccup mode.
During this mode, the high-side MOSFET and low-side driver are
both turned off. The device remains in this mode for seven soft
start cycles and then attempts to restart from soft start. If the
current-limit fault is cleared, the device resumes normal
operation; otherwise, it reenters hiccup mode.
The
FET voltage exceeds the negative current-limit threshold voltage
(50 mV typical), the low-side FET turns off immediately for the
remainder of this cycle. Both the high-side and low-side FETs
turn off until the next cycle.
In some cases, the input voltage (PVIN) ramp rate is too slow
or the output capacitor is too large to support the set regulation
voltage during the soft start, causing the device to enter the
hiccup mode. To prevent such cases, use a resistor divider at the
ENx pin to program the UVLO of the input voltage or use a
longer soft start time.
VOLTAGE TRACKING
The
voltage to track an external (master) voltage. Voltage tracking
allows power sequencing applicable for FPGAs, DSPs, and ASICs,
which may require a power sequence between the core and the I/O
voltages.
The internal error amplifier includes three positive inputs: the
internal reference voltage, the soft start voltage, and the tracking
input voltage. The error amplifier regulates the feedback voltage
to the lowest of the three voltages. To track a master voltage,
connect the TRKx pin to a resistor divider from the master
voltage, as shown in Figure 47.
ADP2325
ADP2325
ADP2325
R
R
TRK_BOT
TRK_TOP
V
MASTER
provides a negative current limit. When the low-side
has a tracking input, TRKx, that allows the output
Figure 47. Voltage Tracking
TRKx
ADP2325
SWx
FBx
R
R
TOP
BOT
V
SLAVE
Rev. 0 | Page 18 of 32
Coincident Tracking
A common application is coincident tracking, which is shown in
Figure 48. Coincident tracking limits the slave output voltage to
be the same as the master voltage until it reaches regulation. To
enable coincident tracking, set R
Ratiometric Tracking
In ratiometric tracking, the slave output voltage is limited to a frac-
tion of the master voltage. In this application, the slave and master
voltages reach their final values at the same time (see Figure 49).
The ratio of the slave output voltage to the master voltage is a
function of the two dividers, as follows:
The final TRKx pin voltage must be higher than 0.54 V. If the
tracking function is not used, connect the TRKx pin to INTVCC.
PARALLEL OPERATION
The
a single output of 10 A. To configure the
single output
1.
2.
3.
During parallel operation, the voltages of PVIN1 and PVIN2
should be the same.
ADP2325
Connect the FB2 pin to INTVCC, thereby disabling the
Channel 2 error amplifier.
Connect COMP1 to COMP2 and connect EN1 to EN2.
Use SS1 to set the soft start time and keep SS2 open.
V
V
MASTER
SLAVE
=
supports a 2-phase parallel operation to provide
1
+
1
Figure 49. Ratiometric Tracking
Figure 48. Coincident Tracking
+
R
R
TRK
TRK
R
R
TOP
BOT
_
_
TOP
BOT
TIME
TIME
TRK_TOP
= R
TOP
ADP2325
V
V
V
V
MASTER
SLAVE
MASTER
SLAVE
and R
Data Sheet
TRK_BOT
as a 2-phase
= R
BOT
.