LTC3832-1ES8#TR Linear Technology, LTC3832-1ES8#TR Datasheet - Page 12

• Manufacturer Part Number: LTC3832-1ES8#TR
• Description: IC CTRLR DC/DC SYNC BUCK 8-SOIC
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3832-1ES8#TR

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 2.5V
• Current - Output: 20A
• Frequency - Switching: 300kHz
• Voltage - Input: 3 ~ 8 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

In many applications, V
through an RC filter. This supply can be as low as 3V. The
low quiescent current (typically 800 A) allows the use of
relatively large filter resistors and correspondingly small
filter capacitors. 100
equate filtering for V
4.7 F bypass capacitor as close to the LTC3832 V
possible.
Gate drive for the top N-channel MOSFET Q1 is supplied
from PV
power supply input) by at least one power MOSFET V
for efficient operation. An internal level shifter allows PV
to operate at voltages above V
mum. This higher voltage can be supplied with a separate
supply, or it can be generated using a charge pump.
Gate drive for the bottom MOSFET Q2 is provided through
PV
This supply only needs to be above the power MOSFET
V
from the same supply/charge pump for the PV
be connected to a lower supply to improve efficiency.
LTC3832/LTC3832-1
APPLICATIO S I FOR ATIO
12
GS(ON)
LTC3832
CC2
LTC3832-1
CIRCUITRY
INTERNAL
CIRCUITRY
V
INTERNAL
for the LTC3832 or V
CC
V
for efficient operation. PV
/PV
CC1
CC
CC2
. This supply must be above V
Figure 7. LTC3832-1 Power Supplies
Figure 6. LTC3832 Power Supplies
PV
CC2
U
CC
. For best performance, connect the
PV
and 4.7 F usually provide ad-
PV
CC
U
CC1
CC1
CC
can be powered from V
CC
/PV
G1
G2
G1
G2
and V
CC2
CC2
W
V
V
IN
IN
for the LTC3832-1.
Q1
Q2
IN
can also be driven
Q1
Q2
, up to 14V maxi-
L
L
O
O
IN
CC1
+
U
(the main
+
, or it can
CC
3832 F6
3832 F7
C
GS(ON)
C
pin as
OUT
OUT
V
V
OUT
CC1
OUT
IN
Figure 8 shows a tripling charge pump circuit that can be
used to provide 2V
top and bottom MOSFETs respectively. These should fully
enhance MOSFETs with 5V logic level thresholds. This
circuit provides 3V
2V
Schottky diodes. The circuit requires the use of Schottky
diodes to minimize forward drop across the diodes at
start-up. The tripling charge pump circuit can rectify any
ringing at the drain of Q2 and provide more than 3V
PV
to PGND to prevent transients from damaging the circuitry
at PV
The charge pump capacitors for PV
G2 pin goes high and the switch node is pulled low by Q2.
The G2 on-time becomes narrow when LTC3832/
LTC3832-1 operates at a maximum duty cycle (95%
typical), which can occur if the input supply rises more
slowly than the soft-start capacitor or if the input voltage
droops during load transients. If the G2 on-time gets so
narrow that the switch node fails to pull completely to
ground, the charge pump voltage may collapse or fail to
start, causing excessive dissipation in external MOSFET,
Q1. This condition is most likely with low V
high switching frequencies, coupled with large external
MOSFETs which slow the G2 and switch node slew rates.
The LTC3832/LTC3832-1 overcome this problem by sens-
ing the PV
2.5V above V
70% by clamping the COMP pin at 1.8V (QC in the Block
IN
CC1
D
12V
1N5242
10 F
– 2V
Z
CC1
; a 12V zener diode should be included from PV
LTC3832
or the gate of Q1.
F
CC1
PV
to PV
1N5817
CC2
CC
voltage when G1 is high. If PV
Figure 8. Tripling Charge Pump
, the maximum G1 duty cycle is reduced to
CC2
PV
1N5817
IN
IN
CC1
where V
G1
G2
– 3V
and 3V
F
0.1 F
to PV
F
IN
is the forward voltage of the
gate drive for the external
1N5817
0.1 F
CC1
CC1
V
while Q1 is ON and
IN
Q1
Q2
refresh when the
CC
CC1
L
O
voltages and
is less than
+
sn3832 3832fs
3832 F08
C
OUT
IN
CC1
V
OUT
at