LTC2924I データシートの表示（PDF） - Linear Technology
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LTC2924I Datasheet PDF : 22 Pages
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LTC2924
Applications Information
a Power On sequence (VON) and Off during a Power Off
sequence (VOFF).
Referring to Figures 5 and 6, each set of resistors can
then be calculated by:
RB
=
VON – VOFF
IHYS
RA
=
RB
VON
• 0.61V
– 0.61V
In the following example (Figure 5) IHYS is 50µA. This
corresponds to a RHYS resistor of:
IHYS
VPS
VON = 2.2V
VOFF = 1V
IHYS RB
IRB
IN
RA
IFB = IRB + IHYS
+– 0.61V
2924 F05
Figure 5. Designing IHYS, Feedback Resistors
RHYS
=
0.5V
50µA
=
10kΩ
In Figure 5, VON = 2.2V and VOFF = 1V. Using the equations
provided above:
RB
=
2.2V – 1V
50µA
=
24kΩ
RA
=
24kΩ • 0.61V
2.2V – 0.61V
=
9.2kΩ
Hysteresis Voltage Check
After calculating the resistors RB and RA, check to make
sure the hystersis voltage at the ON and IN1-IN4 pins is
greater than 4mV. Use the following equation:
VHYS
=
(VON – VOFF )
RA +RB
• RA
For this example :
VHYS
=
(2.2V – 1V) • 9.2kΩ
9.2kΩ + 24kΩ
=
0.33V
which is greater than 4mV.
POWER SUPPLY 1
3.3V
SHDN
POWER SUPPLY 2
5V
SHDN
POWER SUPPLY 3
1.6V
SHDN
5V EARLY*
POWER SUPPLY 4
2.5V
SHDN
0.1µF
10k 10k
SYSTEM
CONTROLLER
*5V EARLY MUST BE ON BEFORE
SEQUENCING SUPPLIES
150nF
150nF
VCC
OUT1
IN1
LTC2924
OUT2
IN2
OUT3
IN3
OUT4
IN4
ON
DONE
FAULT
TMR
HYS/CFG
PGT GND
VON ≥ 3.01V
VOFF ≤ 2.68V
VON ≥ 4.49V
VOFF ≤ 3.99V
VON ≥ 1.43V
VOFF ≤ 1.27V
VON ≥ 2.25V
VOFF ≤ 2V
24.9k 15.8k 49.9k 33.2k
9.31k 11.81k 7.87k 8.45k
49.9k
2924 TA03
Figure 6. Typical Power Supply Sequencer
For more information www.linear.com/LTC2924
2924fc
11
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