LTC3890EGN-1#TRPBF Linear Technology, LTC3890EGN-1#TRPBF Datasheet - Page 21

• Manufacturer Part Number: LTC3890EGN-1#TRPBF
• Description: IC BUCK SYNC ADJ DUAL 28SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3890EGN-1#TRPBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.8 ~ 24 V
• Frequency - Switching: 350kHz ~ 535kHz
• Voltage - Input: 4 ~ 60 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -

pin is less than 4.7V, the V
sipation for the IC in this case is highest and is equal to
V
operating frequency as discussed in the Efficiency Con-
siderations section. The junction temperature can be
estimated by using the equations given in Note 3 of the
Electrical Characteristics. For example, the LTC3890-1
INTV
supply when not using the EXTV
ent temperature:
To prevent the maximum junction temperature from be-
ing exceeded, the input supply current must be checked
while operating in forced continuous mode (PLLIN/MODE
= INTV
When the voltage applied to EXTV
V
EXTV
EXTV
to regulate the INTV
is less than 5.1V, the LDO is in dropout and the INTV
voltage is approximately equal to EXTV
is greater than 5.1V, up to an absolute maximum of 14V,
INTV
Using the EXTV
control power to be derived from one of the LTC3890-1’s
switching regulator outputs (4.7V ≤ V
normal operation and from the V
put is out of regulation (e.g., start-up, short-circuit). If
more current is required through the EXTV
is specified, an external Schottky diode can be added
between the EXTV
not apply more than 6V to the EXTV
that EXTV
Significant efficiency and thermal gains can be realized
by powering INTV
rent resulting from the driver and control currents will be
scaled by a factor of (Duty Cycle)/(Switcher Efficiency).
For 5V to 14V regulator outputs, this means connecting
the EXTV
APPLICATIONS INFORMATION
IN
IN
T
LDO is turned off and the EXTV
J
• I
CC
CC
CC
CC
= 70°C + (15mA)(40V)(90°C/W) = 125°C
INTVCC
CC
is regulated to 5.1V.
current is limited to less than 15mA from a 40V
LDO remains on as long as the voltage applied to
remains above 4.5V. The EXTV
) at maximum V
CC
CC
pin directly to V
. The gate charge current is dependent on
≤ V
CC
IN
.
CC
CC
LDO allows the MOSFET driver and
CC
from the output, since the V
and INTV
voltage to 5.1V, so while EXTV
IN
IN
.
OUT
LDO is enabled. Power dis-
CC
. Tying the EXTV
CC
CC
CC
IN
pins. In this case, do
supply at 70°C ambi-
CC
rises above 4.7V, the
LDO is enabled. The
LDO when the out-
OUT
pin and make sure
CC
CC
. When EXTV
≤ 14V) during
LDO attempts
CC
LDO than
CC
IN
pin to
cur-
CC
CC
CC
an 8.5V supply reduces the junction temperature in the
previous example from 125°C to:
However, for 3.3V and other low voltage outputs, additional
circuitry is required to derive INTV
The following list summarizes the four possible connec-
tions for EXTV
1. EXTV
2. EXTV
3. EXTV
4. EXTV
T
from the internal 5.1V regulator resulting in an efficiency
penalty of up to 10% at high input voltages.
connection for a 5V to 14V regulator and provides the
highest efficiency.
supply is available in the 5V to 14V range, it may be
used to power EXTV
the MOSFET gate drive requirements. Ensure that
EXTV
For 3.3V and other low voltage regulators, efficiency
gains can still be realized by connecting EXTV
output-derived voltage that has been boosted to greater
than 4.7V. This can be done with the capacitive charge
pump shown in Figure 9. Ensure that EXTV
J
= 70°C + (15mA)(8.5V)(90°C/W) = 82°C
EXTV
1/2 LTC3890-1
CC
CC
CC
CC
CC
Figure 9. Capacitive Charge Pump for EXTV
CC
Connected to an Output-Derived Boost Network.
Grounded. This will cause INTV
Connected directly to V
Connected to an External supply. If an external
< V
PGND
TG1
BG1
CC
IN
V
SW
C
IN
.
IN
:
MTOP
MBOT
CC
providing it is compatible with
BAT85
D
L
CC
OUT
power from the output.
NDS7002
LTC3890-1
R
SENSE
. This is the normal
CC
to be powered
38901 F09
CC
CC
BAT85
BAT85
C
V
OUT
OUT
CC
< V
21
to an
38901fa
IN
.