Datasheet

LTC3859A
6
3859af
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 LTC3859A is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3859AE is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3859AI is guaranteed
over the –40°C to 125°C operating junction temperature range, the
LTC3859AH is guaranteed over the –40°C to 150°C operating junction
temperature range and the LTC3859AMP is tested and guaranteed over
the –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. T
J
is calculated from
the ambient temperature T
A
and power dissipation P
D
according to the
following formula: T
J
= T
A
+ (P
D
• q
JA
), where q
JA
= 34°C/W for the QFN
package and q
JA
= 25°C/W for the TSSOP package.
Note 3: This IC includes overtermperature 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 LTC3859A is tested in a feedback loop that servos V
ITH1,2,3
to a specified voltage and measures the resultant V
FB
. The specification at
85°C is not tested in production and is assured by design, characterization
and correlation to production testing at other temperatures (125°C for the
LTC3859AE/LTC3859AI, 150°C for the LTC3859AH/LTC3859AMP). For the
LTC3859AMP, the specification at –40°C is not tested in production and is
assured by design, characterization and correlation to production testing
at –55°C.
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See the Applications Information
section.
Note 6: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7: The minimum on-time condition is specified for an inductor
peak-to-peak ripple current ≥ 40% of I
MAX
(See the Minimum On-Time
Considerations in the Applications Information section).
elecTrical characTerisTics
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
T
PG1
Delay For Reporting a Fault 20 µs
OV3 Boost Overvoltage Indicator Output
V
OV3L
OV3 Voltage Low I
OV3
= 2mA 0.2 0.4 V
I
OV3
OV3 Leakage Current V
OV3
= 5V ±1 µA
V
OV
OV3 Trip Level V
FB
With Respect to Set Regulated Voltage 6 10 13 %
Hysteresis 1.5 %
BOOST3 Charge Pump
I
BST3
BOOST3 Charge Pump Available Output
Current
V
BOOST3
= 16V; V
SW3
= 12V;
Forced Continuous Mode
65 µA
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
BIAS
= 12V, V
RUN1,2,3
= 5V, EXTV
CC
= 0V unless otherwise
noted. (Note 2)