LTC3787
4
3787fc
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
INTV
CC
Linear Regulator
V
INTVCC(VIN)
Internal V
CC
Voltage 6V < V
BIAS
< 38V, V
EXTVCC
= 0 5.2 5.4 5.6 V
VLDO INT INTV
CC
Load Regulation I
CC
= 0mA to 50mA 0.5 2 %
V
INTVCC(EXT)
Internal V
CC
Voltage V
EXTVCC
= 6V 5.2 5.4 5.6 V
VLDO EXT INTV
CC
Load Regulation I
CC
= 0mA to 40mA, V
EXTVCC
= 6V 0.5 2 %
V
EXTVCC
EXTV
CC
Switchover Voltage EXTV
CC
Ramping Positive
l
4.5 4.8 5 V
V
LDOHYS
EXTV
CC
Hysteresis 250 mV
Oscillator and Phase-Locked Loop
f
PROG
Programmable Frequency R
FREQ
= 25k
R
FREQ
= 60k
R
FREQ
= 100k
335
105
400
760
465
kHz
kHz
kHz
f
LOW
Lowest Fixed Frequency V
FREQ
= 0V 320 350 380 kHz
f
HIGH
Highest Fixed Frequency V
FREQ
= INTV
CC
488 535 585 kHz
f
SYNC
Synchronizable Frequency PLLIN/MODE = External Clock
l
75 850 kHz
PGOOD Output
V
PGL
PGOOD Voltage Low I
PGOOD
= 2mA 0.2 0.4 V
I
PGOOD
PGOOD Leakage Current V
PGOOD
= 5V ±1 µA
V
PGOOD
PGOOD Trip Level V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Negative
Hysteresis
–12 –10
2.5
–8 %
%
V
FB
Ramping Positive
Hysteresis
810
2.5
12 %
%
t
PGOOD(DELAY)
PGOOD Delay PGOOD Going High to Low 25 µs
BOOST1 and BOOST2 Charge Pump
I
BOOST1,2
BOOST Charge Pump Available Output
Current
V
SW1,2
= 12V; V
BOOST1,2
– V
SW1,2
= 4.5V;
FREQ = 0V, Forced Continuous or
Pulse-Skipping Mode
55 µA
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C, VBIAS = 12V, unless otherwise noted (Note 2).
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3787 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3787E is guaranteed to meet specifications from
0°C to 85°C junction temperature. Specifications over the –40°C to
125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC3787I is guaranteed over the –40°C to 125°C operating junction
temperature range, the LTC3787H is guaranteed over the –40°C to 150°C
operating temperature range and the LTC3787MP is tested and guaranteed
over the full –55°C to 150°C operating junction temperature range. High
junction temperatures degrade operating lifetimes; operating lifetime
is derated for junction temperatures greater than 125°C. Note that the
maximum ambient temperature consistent with these specifications is
determined by specific operating conditions in conjunction with board
layout, the rated package thermal impedance and other environmental
factors. The junction temperature (T
J
, in °C) is calculated from the ambient
temperature (T
A
, in °C) and power dissipation (P
D
, in Watts) according to
the formula: T
J
= T
A
+ (P
D
• θ
JA
), where θ
JA
= 43°C/W for the QFN package
and θ
JA
= 90°C/W for the SSOP package.
Note 3: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device.
Note 4: The LTC3787 is tested in a feedback loop that servos V
FB
to the
output of the error amplifier while maintaining I
TH
at the midpoint of the
current limit range.
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 6: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7: see Minimum On-Time Considerations in the Applications
Information section.
