MIC2085 Datasheet, PDF (3/29 Pages) Micrel Semiconductor – Single Channel Hot Swap Controllers

Micrel, Inc.
MIC2085/2086
Pin Description (Cont.)
Pin Number
MIC2086
4
5
6
7
8
9, 10
11
12
13
14
15
16
17
Pin Number
MIC2085
4
5
NA
6
7
8
9
10
11
12
Na
13
14
Pin Name Pin Function
ON
/POR
PWRGD
/FAULT
FB
GND
OV
COMPOUT
COMP+
COMP-
DIS
REF
GATE
ON Input: Active high. The ON pin, an input to a Schmitt-triggered comparator
used to enable/disable the controller, is compared to a V_TH reference with
100mV of hysteresis. Once a logic high is applied to the ON pin (V_ON > 1.24V), a
start-up sequence is initiated as the GATE pin starts ramping up towards its final
operating voltage. When the ON pin receives a low logic signal (V_ON < 1.14V),
the GATE pin is grounded and /FAULT is high if VCC is above the UVLO
threshold. ON must be low for at least 20µs in order to initiate a start-up
sequence. Additionally, toggling the ON pin LOW to HIGH resets the circuit
breaker.
Power-On Reset Output: Open drain N-Channel device, active low. This pin
remains asserted during start-up until a time period t_POR after the FB pin voltage
rises above the power-good threshold (VFB). The timing capacitor CPOR
determines t_POR. When an output undervoltage condition is detected at the FB
pin, /POR is asserted for a minimum of one timing cycle, t_POR. The /POR pin has
a weak pull-up to VCC
Power-Good Output: Open drain N-Channel device, active high. When the
voltage at the FB pin is lower than 1.24V, the PWRGD output is held low. When
the voltage at the FB pin is higher than 1.24V, then PWRGD is asserted. A pull-
up resistor connected to this pin and to VCC will pull the output up to VCC. The
PWRGD pin has a weak pull-up to VCC.
Circuit Breaker Fault Status Output: Open drain N-Channel device, active low.
The /FAULT pin is asserted when the circuit breaker trips due to an overcurrent
condition. Also, this pin indicates undervoltage lockout and overvoltage fault
conditions. The /FAULT pin has a weak pull-up to VCC.
Power-Good Threshold Input: This input is internally compared to a 1.24V
reference with 3mV of hysteresis. An external resistive divider may be used to
set the voltage at this pin. If this input momentarily goes below 1.24V, then /POR
is activated for one timing cycle, t_POR, indicating an output undervoltage
condition. The /POR signal de-asserts one timing cycle after the FB pin exceeds
the power-good threshold by 3mV. A 5µs filter on this pin prevents glitches from
inadvertently activating this signal.
Ground Connection: Tie to analog ground
OV Input: When the voltage on OV exceeds its trip threshold, the GATE pin is
pulled low and the CRWBR timer starts. If OV remains above its threshold long
enough for CRWBR to reach its trip threshold, the circuit breaker is tripped.
Otherwise, the GATE pin begins to ramp up one POR timing cycle after OV
drops below its trip threshold.
Uncommitted Comparator’s Open Drain Output.
Comparator’s Non-Inverting Input.
Comparator’s Inverting Input.
Discharge Output: When the MIC2086 is turned off, a 550Ω internal resistor at
this output allows the discharging of any load capacitance to ground.
Reference Output: 1.24V nominal. Tie a 0.1µF capacitor to ground to ensure
stability.
Gate Drive Output: Connects to the gate of an external N-Channel MOSFET. An
internal clamp ensures that no more than 13V is applied between the GATE pin
and the source of the external MOSFET. The GATE pin is immediately brought
low when either the circuit breaker trips or an undervoltage lockout condition
occurs.
May 2006
3
M9999-050406
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