MIC2589 Micrel Semiconductor, MIC2589 Datasheet - Page 14

• Manufacturer Part Number: MIC2589
• Description: (MIC2589 / MIC2595) SINGLE-CHANNEL NEGATIVE HIGH VOLTAGE HOT SWAP POWER CONTROLLERS/SEQUENCERS
• Manufacturer: Micrel Semiconductor

MIC2589/2595
The closest standard 1% values for R2 = 11.8k . Lastly, the
value for R1 is calculated:
The closest standard 1% value for R1 = 698k .
Using standard 1% resistor values, the circuit’s nominal
UV and OV thresholds are:
Programmable UVLO Hysteresis (MIC2595 and
MIC2595R)
The MIC2595 and the MIC2595R devices have user-pro-
grammable hysteresis by means of the ON and OFF pins
(Pins 4 and 3, respectively). This allows setting the
MIC2595/95R to turn on at a voltage V1, and not turn off until
a second voltage V2, where V2 < V1. This can significantly
simplify dealing with source impedances in the supply buss
while at the same time increasing the amount of available
operating time from a loosely regulated power rail (for ex-
ample, a battery supply). The MIC2595/95R holds the output
off until the voltage at the ON pin is above its V
value given in the “Electrical Characteristics” table. Once the
output has been enabled by the ON pin, it will remain on until
the voltage at the OFF pin falls below its respective V
threshold value, or the part turns off due to an external fault
condition. Should either event occur, the GATE pin is imme-
diately pulled low and will remain low until the ON pin voltage
once again above its V
and turn-off voltage levels are set using the resistor divider
R1, R2, and R3 as shown in the “Typical Application” where
the equations to set the trip points are shown below. For the
following example, the circuit’s ON threshold is set to V
40V and the circuit’s OFF threshold is set to
V
M9999-031504
OFF
V
V
UV
OV
= 35V.
R2 = R3
R2 12.4k
R1= R3
R1= 12.4k
R1= 705.81k
= 36.5V
= 71.2V
V
V
V
OV
OV
UV
1.223V
72V – 1.223V
– 1.223V
72V
37V
ONH
– 1
1.223V
threshold. The circuit’s turn-on
– 1
– R2
11.73k
– R2
ONH
threshold
OFFL
ON
=
14
Given V
two resistor values can be readily determined. A suggested
value for R3 is that which will provide approximately 100 A of
current through the voltage divider chain at V
yields the following as a starting point:
The closest standard 1% value for R3 = 12.4k . Solving for
R2 and R1 yields:
The closest standard 1% value for R2 = 1.78 k . Lastly, the
value for R1 is calculated:
The closest standard 1% value for R1 = 392k .
Using standard 1% resistor values, the circuit’s nominal
ON and OFF thresholds are:
V
V
ON
OFF
R1 = 391.38k
R3
R2 = R3
R2 = 12.4k
R1= R3
R1= 12.4k
V
V
ON
OFF
OFF
= 40.1V
= 35V
V
, V
V
OFFL
100 A
V
ONH
ON
OFFL
V
, and any one resistor value, the remaining
(typ)
ON
(typ)
V
V
OFF
1.223V
(typ)
ON
40V – 1.223V
– 1.223V
40V
35V
1.223V
1.223V
100 A
– 1
R1 R2 R3
R1 R2 R3
– 1
R2 + R3
R3
– R2
1.77k
12.23k
– R2
DD
= V
March 2004
OFF
Micrel
. This