LTC3788
4
3788fc
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
t
ON(MIN)
Minimum BG On-Time (Note 7) 110 ns
INTV
CC
Linear Regulator
V
INTVCCVIN
Internal V
CC
Voltage 6V < VBIAS < 38V, V
EXTVCC
= 0V 5.2 5.4 5.6 V
V
LDOVIN
INTV
CC
Load Regulation I
CC
= 0mA to 50mA, V
EXTVCC
= 0V 0.5 2 %
V
INTVCCEXT
Internal V
CC
Voltage V
EXTVCC
= 6V 5.2 5.4 5.6 V
V
LDOEXT
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 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 105 kHz
R
FREQ
= 60k 335 400 465 kHz
R
FREQ
= 100k 760 kHz
f
LOW
Lowest Fixed Frequency V
FREQ
= 0V 320 350 380 kHz
f
HIGH
Highest Fixed Frequency V
FREQ
= INTV
CC
485 535 585 kHz
f
SYNC
Synchronizable Frequency PLLIN/MODE = External Clock
l
75 850 kHz
PGOOD1 and PGOOD2 Outputs
V
PGL
PGOOD Voltage Low I
PGOOD
= 2mA 0.2 0.4 V
I
PGOOD
PGOOD Leakage Current V
PGOOD
= 5V ±1 µA
V
PG
PGOOD Trip Level V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Negative –12 –10 –8 %
Hysteresis 2.5 %
V
FB
Ramping Positive 8 10 12 %
Hysteresis 2.5 %
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 full 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 LTC3788 is tested under pulsed load conditions such that T
J
≈ T
A
. The LTC3788E 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 LTC3788I is guaranteed
over the –40°C to 125°C operating junction temperature range. 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
= 34°C/W.
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 LTC3788 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.
