LTC1430IS Linear Technology, LTC1430IS Datasheet - Page 10

• Manufacturer Part Number: LTC1430IS
• Description: IC SW REG CNTRLR STEP-DWN 16SOIC
• Manufacturer: Linear Technology

Specifications of LTC1430IS

• Applications: Controller, Intel Pentium®
• Voltage - Input: 4 ~ 8 V
• Number Of Outputs: 1
• Voltage - Output: 3.3V, Adjustable
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIO S I FOR ATIO
LTC1430
OS-CON part number 10SA220M (220 F/10V) capacitors
feature 2.3A allowable ripple current at 85 C and 0.035
ESR; three in parallel at the input and six at the output will
meet the above requirements.
Input Supply Considerations/Charge Pump
The 16-lead LTC1430 requires four supply voltages to
operate: PV
for MOSFET gate drive and a clean, low ripple V
LTC1430 internal circuitry (Figure 6). In many applica-
tions, PV
a common high power supply, provided that the supply
voltage is high enough to fully enhance the gate of external
MOSFET M2. This can be the 5V system supply if a logic
level MOSFET is used for M2. V
with an RC from this same high power supply; the low
quiescent current (typically 350 A) allows the use of
relatively large filter resistors and correspondingly small
filter capacitors. 100
equate filtering for V
The 8-lead versions of the LTC1430 have the PV
V
pin, brought out as V
requirements as the 16-lead part, but must also be able to
supply the gate drive current to M2. This can be obtained
by using a larger RC filter from the PV
work well here. The 10 F capacitor must be VERY close to
the part (preferably right underneath the unit) or output
regulation may suffer.
10
CC
LTC1430 (16-LEAD)
pins tied together inside the package (Figure 7). This
CIRCUITRY
INTERNAL
V
CC
CC
CC
and PV
Figure 6. 16-Lead Power Supplies
for the main power input, PV
PV
CC2
CC2
U
CC
CC
.
can be tied together and fed from
/PV
PV
and 4.7 F usually provide ad-
U
CC1
CC2
G1
G2
, has the same low ripple
CC
can usually be filtered
PV
W
CC
CC
M1
M2
pin; 22 and 10 F
L1
CC1
+
and PV
U
CC
CC2
C
for the
LTC1430 • F06
OUT
V
and
OUT
CC2
For both versions of the LTC1430, PV
than PV
enhance the gate of M1. This higher voltage can be
provided with a separate supply (typically 12V) which
should power up after PV
simple charge pump (Figure 4). The charge pump consists
of a 1N4148 diode from PV
capacitor from PV
M2. This circuit provides 2PV
ON and PV
voltage of the 1N4148 diode. Ringing at the drain of M2
can cause transients above 2PV
higher than 7V, a 12V zener diode should be included from
PV
circuitry at PV
More complex charge pumps can be constructed with the
16-lead versions of the LTC1430 to provide additional
voltages for use with standard threshold MOSFETs or very
low PV
provide 2PV
nected to PV
dard threshold MOSFETs to be used with 5V at PV
logic level threshold MOSFETs to be used with 3.3V at
PV
allowing the entire system to run from a single 3.3V
supply. Tripling charge pumps require the use of Schottky
diodes to minimize forward drop across the diodes at
start-up. The tripling charge pump circuit will tend to
rectify any ringing at the drain of M2 and can provide well
more than 3PV
ing factor) circuits should include a 12V zener clamp diode
D
Z
CC1
CC
LTC1430 (8-LEAD)
to prevent overvoltage at PV
CIRCUITRY
. V
V
INTERNAL
CC
to PGND to prevent transients from damaging the
CC
CC
CC
/PV
voltages. A tripling charge pump (Figure 5) can
CC2
can be driven from the same potential as PV
by at least one external MOSFET V
CC
CC
CC2
Figure 7. 8-Lead Power Supplies
CC2
– V
CC
and 3PV
and PV
at PV
CC1
F
or the gate of M1.
while M1 is OFF where V
to the switching node at the drain of
CC1
PV
CC
CC1
CC
CC1
; all tripling (or higher multiply-
, or it can be generated with a
voltages. These can be con-
respectively, allowing stan-
CC
CC
G1
G2
CC1
– V
CC
to PV
PV
F
.
at PV
to PV
CC
M1
M2
CC1
CC1
L1
must be higher
CC1
CC1
GS(ON)
and a 0.1 F
; if PV
F
while M1 is
+
is the ON
CC
C
to fully
OUT
LTC1430 • F07
or 5V
CC
V
CC2
OUT
is
,