MIC2582_09 Datasheet, PDF (15/25 Pages) Micrel Semiconductor – Single Channel Hot Swap Controllers

Micrel, Inc.
current (I_CPOR) are typically 1.24V and 2.5µA,
respectively.
For the MIC2583/83R, a capacitor connected to
CFILTER is used to set the timer which activates the
circuit breaker during overcurrent conditions. When the
voltage across the sense resistor exceeds the slow trip
current limit threshold of 50mV, the overcurrent timer
begins to charge for a time period (t_OCSLOW), determined
by C_FILTER. When no capacitor is connected to CFILTER
and for the MIC2582, t_OCSLOW defaults to 5µs. If t_OCSLOW
elapses, then the circuit breaker is activated and the
GATE output is immediately pulled to ground. For the
MIC2583/83R, the following equation is used to
determine the overcurrent timer period, t_OCSLOW.
t_OCSLOW
=
C_FILTER
×
V_TH
I_TIMER
≅ 0.19 × C_FILTER
(μF )
(8)
where V_TH, the CFILTER timer threshold, is 1.24V and
I_TIMER, the overcurrent timer current, is 6.5µA. Tables 2
and 3 provide a quick reference for several timer
calculations using select standard value capacitors.
MIC2582/MIC2583
C_POR
0.01µF
0.02µF
0.033µF
0.05µF
0.1µF
0.33µF
0.47µF
1µF
t_START
1.2ms
2.4ms
4ms
6ms
12ms
40ms
56ms
120ms
t_POR
5ms
10ms
16.5ms
25ms
50ms
165ms
235ms
500ms
Table 2. Selected Power-On Reset and Start-Up Delays
C_FILTER
680pF
2200pF
4700pF
8200pF
0.033µF
0.1µF
0.22µF
0.47µF
t_OCSLOW
130µs
420µs
900µs
1.5ms
6ms
19ms
42ms
90ms
Table 3. Selected Overcurrent Timer Delays
April 2009
15
M9999-043009-C