![](http://datasheet.mmic.net.cn/230000/LM5642_datasheet_15593135/LM5642_6.png)
Electrical Characteristics
(Continued)
Unless otherwise specified, V
= 28V, GND = PGND = 0V, VLIN5 = VDD1 = VDD2. Limits appearing in
boldface
type apply
over the specified operating junction temperature range, (-40C to +125C, if not otherwise specified). Specifications appearing
in plain type are measured using low duty cycle pulse testing with T
A
= 25C (Note 6), (Note 7). Min/Max limits are guaranteed
by design, test, or statistical analysis.
Symbol
GI
SNS1
,
GI
SNS2
Voltage References and Linear Voltage Regulators
UVLO
VLIN5 Under-voltage
Lockout
Threshold Rising
Parameter
Conditions
Min
Typ
Max
Units
Current Sense Amplifier
(1&2) Gain
V
COMPx
= 1.25V
4.2
5.2
7.5
ON/SS1, ON/SS2 transition
from low to high
3.6
4.0
4.4
V
Note 1:
Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Range indicates conditions for which the device is
intended to be functional, but does not guarantee specfic performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
The guaranteed specifications apply only for the test conditions. Some performance characteristics may degrade when the device is not operated under the listed
test conditions.
Note 2:
ON/SS1 and ON/SS2 are internally pulled up to one diode drop above VLIN5. Do not apply an external pull-up voltage to these pins. It may cause damage
to the IC.
Note 3:
The maximum allowable power dissipation is calculated by using P
= (T
- T
)/
θ
, where T
is the maximum junction temperature, T
is the
ambient temperature and
θ
is the junction-to-ambient thermal resistance of the specified package. The 1.1W rating results from using 125C, 25C, and 90.6C/W
for T
, T
, and
θ
respectively. A
θ
of 90.6C/W represents the worst-case condition of no heat sinking of the 28-pin TSSOP. A thermal shutdown will occur
if the temperature exceeds the maximum junction temperature of the device.
Note 4:
For detailed information on soldering plastic small-outline packages, refer to the
Packaging Databook
available from National Semiconductor Corporation.
Note 5:
For testing purposes, ESD was applied using the human-body model, a 100pF capacitor discharged through a 1.5k
resistor.
Note 6:
A typical is the center of characterization data measured with low duty cycle pulse tsting at T
A
= 25C. Typicals are not guaranteed.
Note 7:
All limits are guaranteed.All electrical characteristics having room-temperature limits are tested during production with T
= T
= 25C.All hot and cold limits
are guaranteed by correlating the electrical characteristics to process and temperature variations and applying statistical process control.
Note 8:
Both switching controllers are off. The linear regulator VLIN5 remains on.
Note 9:
When SS1 and SS2 pins are charged above this voltage and either of the output voltages at Vout1 or Vout2 is still below the regulation limit, the under
voltage protection feature is initialized.
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