LTC3446
4
3446ff
elecTrical characTerisTics
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 LTC3446 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3446E is guaranteed to meet performance specifications
from 0°C to 85°C operating 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 LTC3446I is guaranteed to meet performance specifications 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
(in °C/W) is the package thermal impedance.
Note 3: Minimum operating V
IN
voltage required for the VLDO regulators
to stay in regulation is:
V
IN
≥ LV
OUT(MAX)
+ 1.4V and V
IN
≥ 2.7V
Note 4: Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 5: The LTC3446 is tested in a feedback loop that connects the
BUCKFB pin to the output of the buck converter’s error amplifier (i.e., the
I
TH
pin).
Note 6: Minimum operating LV
IN
voltage required for the VLDO regulators
to stay in regulation is:
LV
IN
≥ L
VOUT(MAX)
+ 100mV and LV
IN
≥ 0.9V
Note 7: 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 8: PGOOD assertion indicates that the feedback voltages of all
enabled supplies are within the specified percentage of their target values.
Note 9: Dropout voltage in the DFN package is assured by design,
characterization and statistical process control.
Buck Regulated Feedback Voltage
vs Temperature
LDO1 Regulated Feedback
Voltage vs Temperature
LDO2 Regulated Feedback
Voltage vs Temperature
TEMPERATURE (°C)
–50
V
BUCKFB
(mV)
800
802
804
110
3446 G01
798
796
792
–10
30
70
–30 130
10
50
90
794
808
806
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 5.5V
TEMPERATURE (°C)
–50
V
LVFB1
(mV)
400
402
404
110
3446 G02
398
396
392
–10
30
70
–30 130
10
50
90
394
408
406
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 5.5V
TEMPERATURE (°C)
–50
V
LVFB2
(mV)
400
402
404
110
3446 G03
398
396
392
–10
30
70
–30 130
10
50
90
394
408
406
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 5.5V
Typical perForMance characTerisTics
