Analog Devices Linear ADI Power LTM4681 Manual page 17

PIN FUNCTIONS
SGND01, SGND23 (F10-F11, U10-U11): SGND is the sig-
nal ground return path of the LTM4681 internal controllers.
SGND is not internally connected to GND. Connect SGND
to GND local to the LTM4681. See recommended layout.
V (A5-A6, B5-B6, C5-C6, D5-D6, E5-E6, F5-F6,
IN01
G5-G6, H5-H6, J5-J6, K5-K6): Positive Power Input to
Channel 0 and 1 Switching Stages. Provide sufficient
decoupling capacitance in the form of multilayer ceramic
capacitors (MLCCs) and low ESR electrolytic (or equiv-
alent) to handle reflected input current ripple from the
step-down switching stage. MLCCs should be placed as
close to the LTM4681 as physically possible. See Layout
Recommendations in the Applications Information
section.
V (N5-N6, P5-P6, R5-R6, T5-T6, U5-U6, V5-V6,
IN23
W5-W6, Y5-Y6, AA5-AA6, AB5-AB6): Positive Power
Input to Channel 2 and 3 Switching Stages. Provide suf-
ficient decoupling capacitance in the form of MLCCs and
low ESR electrolytic (or equivalent) to handle reflected
input current ripple from the step-down switching stage.
MLCCs should be placed as close to the LTM4681 as
physically possible. See Layout Recommendations in the
Applications Information section.
SW0 (C1-C2, D1-D2, E1-E2): Switching Node of Channel
0 Step-Down Converter Stage. Used for test purposes
or EMI-snubbing. May be routed a short distance to a
local test point to monitor switching action of channel
0, if desired, but do not route near any sensitive signals;
otherwise, leave electrically isolated (open).
SW1 (G1-G2, H1-H2, J1-J2): Switching Node of Channel
1 Step-Down Converter Stage. Used for test purposes
or EMI-snubbing. May be routed a short distance to a
local test point to monitor switching action of channel
1, if desired, but do not route near any sensitive signals;
otherwise, leave open.
SW2 (P1-P2, R1-R2, T1-T2): Switching Node of Channel
2 Step-Down Converter Stage. Used for test purposes
or EMI-snubbing. May be routed a short distance to a
local test point to monitor switching action of channel
2, if desired, but do not route near any sensitive signals;
otherwise, leave open.
SW3 (V1-V2, W1-W2, Y1-Y2): Switching Node of Channel
3 Step-Down Converter Stage. Used for test purposes or
EMI-snubbing. May be routed a short distance to a local
test point to monitor switching action of channel 3, if
desired, but do not route near any sensitive signals; oth-
erwise, leave open.
SV (J8): Input Supply for LTM4681's Internal Control
IN_01
IC for channel 0 and 1. In most applications, SV
nects to V
supply separate from V
a lower supply like 6V. The SV
1Ω and 1µF decoupling capacitor. The 1Ω resistor is used
to measure the actual control chip current. See MFR_
READ_ICHIP and MFR_ADC_CONTROL COMMAND sec-
tion. When operating from 4.5V to 5.75V with no auxiliary
bias supply, then the main input supply should connect to
SV and INTV
IN_01
In this configuration, the ICHIP current will not be relevant
since INTV
SV (P11): Input Supply for LTM4681's Internal
IN_23
Control IC for channel 2 and 3. In most applications,
SV connects to V
IN_23
an auxiliary supply separate from V
V from a lower supply like 6V. The SV
IN23
an offboard 1Ω and 1µF decoupling capacitor. The 1Ω
resistor is used to measure the actual control chip cur-
rent. See MFR_READ_ICHIP and MFR_ADC_CONTROL
COMMAND section. When operating from 4.5V to 5.75V
with no auxiliary bias supply, then the main input sup-
ply should connect to SV
Circuit 2 for an example. In this configuration, the I
current will not be relevant since INTV
to SV
IN_23
V
IN_VBIAS
tor that produces 5.5V (V
controllers to reduce power dissipation after power up.
Each internal controller has an INTV
regulator that is powered from SV
eliminate this power loss through these linear regulators,
the V
BIAS
For more information www.analog.com
. SV can be operated from an auxiliary
IN01 IN_01
for powering the V
IN01
IN_01
. See Test Circuit 2 for an example.
CC_01
is connected to SV
CC_01
. SV
IN_23 IN_23
and INTV
IN_23
.
(N9): Input pin to the internal step down regula-
pin) to power both internal
BIAS
powers both at very high efficiency.
LTM4681
con-
IN_01
from
IN01
pin has an offboard
.
IN_01
can be operated from
for powering the
IN23
pin has
IN_23
. See Test
CC_23
CHIP
is connected
CC_23
or INTV
CC_01 CC_23
or SV . To
IN_01 IN_23
Rev. A
17