4
LTC1844 Series
1844fa
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
OUT
+ 0.5V, unless otherwise noted. (Note 2)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
LTC1844-1.5 I
OUT
= 50mA ● 115 160 mV
I
OUT
= 150mA ● 350 450 mV
LTC1844-BYP I
OUT
= 50mA ● 45 75 mV
I
OUT
= 150mA ● 135 200 mV
LTC1844-SD I
OUT
= 50mA ● 45 75 mV
I
OUT
= 150mA ● 135 200 mV
I
LIM
Output Current Limit ● 160 350 mA
e
n
Output Voltage Noise f = 10Hz to 100kHz, C
BP
= 0.1µF, C
OUT
= 10µF, I
L
= 150mA 60 µV
RMS
f = 10Hz to 100kHz, C
BP
= 0.1µF, C
OUT
= 1µF, I
L
= 150mA 65 µV
RMS
V
SHDN
SHDN Input Threshold ● 0.35 0.65 0.9 V
t
DELAY
Shutdown Exit Delay C
BP
= 0.01µF, C
OUT
= 1µF, No load 70 100 µs
C
BP
= 0.01µF, C
OUT
= 1µF, No load ● 200 µs
T
SHDN
Thermal Shutdown Limit 155 °C
∆T
SHDN
Thermal Shutdown Hysteresis 10 °C
I
ADJ
ADJ Pin Bias Current (Notes 3, 8) ● 30 100 nA
I
IRL
Input Reverse Leakage Current LTC1844-3.3, LTC1844-2.8, LTC1844-2.5, LTC1844-1.8, ● 200 500 µA
LTC1844-1.5, V
IN
= –5V, V
OUT
= 0V
LTC1844-BYP, LTC1844-SD, V
IN
= –5V, V
OUT
= 0V ● 1000 1500 µA
I
ORL
Output Reverse Leakage Current V
IN
= 0V, V
OUT
= V
OUT(NOMINAL)
0.01 0.1 µA
(Note 9) V
IN
= 0V, V
OUT
= V
OUT(NOMINAL)
● 1.2 µA
V
OSH
Start-Up Overshoot R
L
= 1k, SHDN Rise Time ≤ 1µs2%V
OUT
V
RP
Output Ripple Rejection (V
IN
– V
OUT
) = 1V (Avg), V
RIPPLE
= 0.5V
P-P
,50dB
f
RIPPLE
= 120Hz, I
LOAD
= 100mA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC1844 is tested and specified under pulse load conditions
such that T
J
≈ T
A
. The LTC1844E is guaranteed to meet performance
specifications from 0°C to 70°C. Specifications over the –40°C to 125°C
operating junction temperature range are assured by design,
characterization and correlation with statistical process controls.
Note 3: The LTC1844 adjustable versions are tested and specified for
these conditions with the ADJ pin connected to the OUT pin for a
V
OUT(NOMINAL)
of 1.25V.
Note 4: Operating conditions are limited by maximum junction
temperature. The regulated output voltage specification will not apply for
all possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range must be
limited. When operating at maximum output current, the input voltage
range must be limited.
Note 5: The LTC1844’s high precision degrades slightly at high
temperatures (T
J
> 70°C) with input voltages below 2.2V. The lower output
voltage versions have been split into higher and lower accuracy input
voltage ranges to reflect this.
Note 6: To ensure adequate input supply voltage, the LTC1844 adjustable
versions are tested and specified for these conditions with an external
resistor divider (two 100k resistors) for an output voltage of 2.50V. The
external resistor divider will add a 5µA load on the output.
Note 7: Dropout voltage is (V
IN
– V
OUT
) when V
OUT
falls to 100mV below
its nominal value measured at V
IN
= V
OUT
+ 0.5V. For example, the
LTC1844-3.3 is tested by measuring the V
OUT
at V
IN
= 3.8V, then V
IN
is
lowered until V
OUT
falls 100mV below the measured value. The difference
(V
IN
– V
OUT
) is then measured and defined as ∆V
DO
.
Note 8: ADJ pin bias current flows into the ADJ pin.
Note 9: Output reverse leakage current is tested with the IN pin grounded
and the OUT pin forced to the rated output voltage.
Note 10: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
