Polyphase Configuration; Connecting The Usb To I 2 C/Smbus/Pmbus Controller To The Ltm4683 In System - Analog Devices LTM4683 Manual

LTM4683
APPLICATIONS INFORMATION
increased by decreasing C
by the same factor that C
quency will be kept the same, thereby keeping the phase
shift the same in the most critical frequency range of the
feedback loop. The gain of the loop will be proportional to
the transconductance of the error amplifier, g
set using bits[7:5] of the MFR_PWM_COMP command.
The output voltage settling behavior is related to the sta-
bility of the closed-loop system and will demonstrate the
actual overall supply performance. A second, more severe
transient is caused by switching in loads with large (>1µF)
supply bypass capacitors. The discharged bypass capaci-
tors are effectively put in parallel with C
rapid drop in V . No regulator can alter its delivery of
OUT
current quickly enough to prevent this sudden step change
in output voltage if the load switch resistance is low and if
it is driven quickly. If the ratio of C
than 1:50, the switch rise time should be controlled so that
the load rise time is limited to approximately 25 • C
Thus, a 10µF capacitor would require a 250µs rise time,
limiting the charging current to about 200mA.

PolyPhase Configuration

When configuring a PolyPhase rail with multiple LTM4683s,
the user must share the SYNC, COMP , SHARE_CLK, FAULT,
USB TO I
64
. If R is increased
COMPna COMP
is decreased, the zero fre-
COMP
, which is
m
, causing a
OUT
to C is greater
LOAD OUT
ADI
100k
CONTROLLER
HEADER
ISOLATED
3.3V
TP0101K
SDA
SCL
TO ADI DC1613A
2
C/SMBus/PMBus
CONTROLLER
TP0101K
VGS MAX ON THE TP0101K IS 8V IF V
CHANGE THE RESISTOR DIVIDER ON THE PFET GATE
LTM4683 HAS TWO INTERNAL CONTROLLERS
Figure 30. Controller Connection
For more information
and ALERT pins of these parts. Be sure to use pull-up resis-
tors on FAULT, SHARE_CLK and ALERT. One of the part's
SYNC pins must be set to the desired switching frequency,
and all other FREQUENCY_SWITCH commands must be
set to External Clock. If an external oscillator is provided,
set the FREQUENCY_SWITCH command to External Clock
for all parts. The relative phasing of all the channels should
be spaced equally. The MFR_RAIL_ADDRESS of all the
devices should be set to the same value.
Multiple channels need to tie all the V
together, and all the V
COMPnb pins together as well. Do not assert bit[4] of
MFR_CONFIG_ALL except in a PolyPhase application. See
the Typical Applications section (Figure 50).
CONNECTING THE USB TO I
CONTROLLER TO THE LTM4683 IN SYSTEM
.
The ADI USB-to-I
LOAD
or equivalent) can be interfaced with the LTM4683 on
the user's board for programming, telemetry, and sys-
tem debugging. The adapter, when used in conjunction
with LTpowerPlay, provides a powerful way to debug an
entire power system. Faults are quickly diagnosed using
telemetry, fault status commands and the fault log. The
V
IN
100k
V
INnn
V
DD33_nn
1µF
10k
SDA_nn
10k
SCL_nn
WP_nn PGND/SGND_nn
V
INnn
V
DD33_nn
1µF
SDA_nn
SCL_nn
> 14V
IN
WP_nn PGND/SGND_nn
www.analog.com
–
pins together, COMPna and
SENSEn
2
C/SMBUS/PMBUS
2
C/SMBus/PMBus adapter
V
DD25_nn
LTM4683
1/2
V
DD25_nn
LTM4683
1/2
4683 F30
+
pins
SENSEn
(DC1613A
Rev. 0