LTC7138
3
7138f
For more information www.linear.com/LTC7138
elecTrical characTerisTics
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 12V, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Supply (V
FB
)
V
FB(ADJ)
Feedback Comparator Threshold
(Adjustable Output)
V
FB
Rising, V
PRG1
= V
PRG2
= 0V
LTC7138E, LTC7138I
LTC7138H, LTC7138MP
l
l
0.792
0.788
0.800
0.800
0.808
0.812
V
V
V
FBH
Feedback Comparator Hysteresis
(Adjustable Output)
V
FB
Falling, V
PRG1
= V
PRG2
= 0V
l
3 5 9 mV
I
FB
Feedback Pin Current V
FB
= 1V, V
PRG1
= V
PRG2
= 0V –10 0 10 nA
V
FB(FIXED)
Feedback Comparator Thresholds
(Fixed Output)
V
FB
Rising, V
PRG1
= SS, V
PRG2
= 0V
V
FB
Falling, V
PRG1
= SS, V
PRG2
= 0V
l
l
4.94
4.91
5.015
4.985
5.09
5.06
V
V
V
FB
Rising, V
PRG1
= 0V, V
PRG2
= SS
V
FB
Falling, V
PRG1
= 0V, V
PRG2
= SS
l
l
3.25
3.23
3.31
3.29
3.37
3.35
V
V
V
FB
Rising, V
PRG1
= V
PRG2
= SS
V
FB
Falling, V
PRG1
= V
PRG2
= SS
l
l
1.78
1.77
1.81
1.80
1.84
1.83
V
V
Operation
I
PEAK
Peak Current Comparator Threshold I
SET
Floating
100k Resistor from I
SET
to GND
I
SET
Shorted to GND
l
l
l
540
270
140
610
310
170
680
350
200
mA
mA
mA
I
VAL
Valley Current Comparator Threshold
Relative to I
PEAK
I
SET
Floating
100k Resistor from I
SET
to GND
I
SET
Shorted to GND
l
l
l
50
45
45
60
60
60
70
70
75
%
%
%
R
ON
Power Switch On-Resistance I
SW
= –100mA 1.8 Ω
I
LSW
Switch Pin Leakage Current V
IN
= 140V, SW = 0V 0.1 1 μA
I
SS
Soft-Start Pin Pull-Up Current V
SS
< 2.5V 4 5 6 μA
t
INT(SS)
Internal Soft-Start Time SS Pin Floating 1 ms
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 LTC7138 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC7138E 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 LTC7138I is guaranteed
over the –40°C to 125°C operating junction temperature range, the
LTC7138H is guaranteed over the –40°C to 150°C operating junction
temperature range and the LTC7138MP 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.
Note 3: 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
is 40°C/W for the MSOP package.
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.
Note 4: 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. The overtemperature protection level is not production tested.
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
