LTC1430 LINER [Linear Technology], LTC1430 Datasheet - Page 4

• Manufacturer Part Number: LTC1430
• Description: High Power Step-Down Switching Regulator Controller
• Manufacturer: LINER [Linear Technology]

PI FU CTIO S
LTC1430
G1 (Pin 1/Pin 1): Driver Output 1. Connect this pin to the
gate of the upper N-channel MOSFET, M1. This output will
swing from PV
is high.
PV
power supply input for G1. G1 will swing from PGND to
PV
PV
using an external supply or a simple charge pump con-
nected to the switching node between the upper MOSFET
and the lower MOSFET; see Applications Information for
details.
PGND (Pin 3/Pin 3): Power Ground. Both drivers return to
this pin. It should be connected to a low impedance ground
in close proximity to the source of M2. 8-lead parts have
PGND and GND tied together at pin 3.
GND (Pin 4/Pin 3): Signal Ground. All low power internal
circuitry returns to this pin. To minimize regulation errors
due to ground currents, GND should be connected to
PGND right at the LTC1430. 8-lead parts have PGND and
GND tied together internally at pin 3.
SENSE
pins connect to the internal resistor divider and to the
internal feedback node. To use the internal divider to set
the output voltage to 3.3V, connect SENSE
terminal of the output capacitor and SENSE
tive terminal. FB should be left floating in applications that
use the internal divider. To use an external resistor divider
to set the output voltage, float SENSE
connect the external resistor divider to FB.
SHDN (Pin 8/Pin 5): Shutdown. A TTL compatible low
level at SHDN for longer than 50 s puts the LTC1430 into
shutdown mode. In shutdown, G1 and G2 go low, all
internal circuits are disabled and the quiescent current
drops to 10 A max. A TTL compatible high level at SHDN
allows the part to operate normally.
SS (Pin 9/NA): Soft-Start. The SS pin allows an external
capacitor to be connected to implement a soft-start func-
tion. An external capacitor from SS to ground controls the
start-up time and also compensates the current limit loop,
allowing the LTC1430 to enter and exit current limit
cleanly. See Applications Information for more details.
4
CC1
CC1
CC
U
. PV
+ V
(Pin 2/Pin 2): Power V
–
, FB, SENSE
GS(ON)
CC1
U
must be connected to a potential of at least
CC1
(M1). This potential can be generated
to PGND. It will always be low when G2
U
+
(Pins 5, 6, 7/Pin 4): These three
(16-Lead Package/8-Lead Package)
CC
for Driver 1. This is the
+
and SENSE
+
to the positive
–
to the nega-
–
and
COMP (Pin 10/Pin 6): External Compensation. The COMP
pin is connected directly to the output of the error amplifier
and the input of the PWM. An RC network is used at this
node to compensate the feedback loop to provide opti-
mum transient response. See Applications Information for
compensation details.
FREQSET (Pin 11/NA): Frequency Set. This pin is used to
set the free running frequency of the internal oscillator.
With the pin floating, the oscillator runs at about 200kHz.
A resistor from FREQSET to ground will speed up the
oscillator; a resistor to V
tions Information for resistor selection details.
I
old for the internal current limit comparator. If I
below I
limit. I
with an external resistor to PV
source.
I
switched node at the source of M1 and the drain of M2
through a 1k resistor. The 1k resistor is required to prevent
voltage transients from damaging I
taken up to 18V above GND without damage.
V
circuits draw their supply from this pin. Connect to a clean
power supply, separate from the main PV
drain of M1. This pin requires a 4.7 F bypass capacitor.
8-lead parts have V
require a 10 F bypass to GND.
PV
power supply input for G2. G2 will swing from GND to
PV
supply. The 8-lead parts have V
at pin 7 and require a 10 F bypass to GND.
G2 (Pin 16/Pin 8): Driver Output 2. Connect this pin to the
gate of the lower N-channel MOSFET, M2. This output will
swing from PV
is high.
MAX
FB
CC
CC2
CC2
(Pin 13/NA): Current Limit Sense. Connect to the
(Pin 14/Pin 7): Power Supply. All low power internal
(Pin 12/NA): Current Limit Set. I
MAX
. PV
(Pin 15/Pin 7): Power V
MAX
CC2
has a 12 A pull-down to GND. It can be adjusted
with G1 on, the LTC1430 will go into current
is usually connected to the main high power
CC2
to PGND. It will always be low when G1
CC
and PV
CC
will slow it down. See Applica-
CC2
CC
CC
CC
tied together at pin 7 and
and PV
for Driver 2. This is the
or an external voltage
FB
MAX
. This pin can be
CC2
sets the thresh-
CC
supply at the
tied together
FB
drops