Datasheet
LTM4618
7
4618fa
NC (A1): No Connect. Leave fl oating.
FREQ (A2): Frequency Selection Pin. An internal low pass
fi lter is tied to this pin. The frequency can be selected with
a voltage from this pin to SGND. A programming resistor
divider can be used to set the operating frequency. The
suggested operating frequency range is 400kHz to 780kHz.
Operating frequencies as low as 250kHz are possible af-
ter evaluating the inductor ripple current for the desired
confi guration. See the Applications Information section.
MODE/PLLIN (A3): Mode Selection or External Synchroni-
zation Pin. Tying this pin to INTV
CC
enables pulse-skipping
operation. Tying this pin low enables forced continuous
mode operation. Burst Mode operation is enabled by fl oat-
ing the pin. A clock on the pin will force the controller into
forced continuous mode of operation and synchronize to
the internal oscillator. The programming DC voltage has
to be removed for clock synchronization.
PGND (BANK 2: A4, B4, D4-D7, E1-E7, F1-F7, G1-G7,
H1-H7, J5-J7, K5, K7, L5-L7, M5-M7): Power ground
pins for both input and output returns.
V
IN
(BANK 1: A5-A7, B5-B7, C5-C7): Power Input Pins.
Apply input voltage between these pins and PGND pins.
Recommend placing input decoupling capacitance directly
between V
IN
pins and PGND pins.
TK/SS (B1): Output Voltage Tracking and Soft-Start Pin. An
internal soft-start current of 1.3µA charges the soft-start
capacitor. See the Applications Information section.
RUN (B2): Run Control Pin. A voltage above 1.35V on
this pin turns on the module. Forcing this pin below 1.1V
will shut down the output. The RUN pin has a 1µA pull-
up current source that increases to 10µA as the RUN pin
voltage reaches 1.5V and up to compliance. Therefore the
pin can be left fl oating for normal operation. A maximum
of 6V can be applied to the pin. A voltage divider can be
used for a UVLO function. See the Applications Informa-
tion section.
SGND (B3, C2 and C3): Signal Ground Pin. Return ground
path for all analog and low power circuitry. Tie a single
connection to PGND. See applications for details.
COMP (C1): Current control threshold and error ampli-
fi er compensation point. The module has been internally
compensated for most I/O ranges.
EXTV
CC
(C4): External Voltage Input. Bypasses the internal
INTV
CC
LDO and powers the internal circuitry and MOSFET
drivers. If a 5V source is available, the internal LDO is
disabled, and the power dissipation is lower, especially at
higher input voltages. See the Applications Information
section.
V
FB
(D1): The negative input of the error amplifi er. Inter-
nally, this pin is connected to V
OUT
with a 60.4k precision
resistor. Different output voltages can be programmed
with an additional resistor between V
FB
and SGND pins.
See applications for details.
PGOOD (D2): Output Voltage Power Good Indicator. Open-
drain logic output that is pulled to ground when the output
voltage is not within ±7.5% of the regulation point.
INTV
CC
(D3): Internal 5V Regulator Output. This pin is for
PIN FUNCTIONS
BCDEFGHJKLAM
1
2
3
4
5
6
7
BANK 1
V
IN
SGND/PGND
CNTRL
BANK 3
SW
BANK 2
PGND
V
OUT