MIC2026-2YMTR Datasheet, PDF (11/16 Pages) Micrel Semiconductor – Dual-Channel Power Distribution Switch

Micrel, Inc.
Block Diagram
MIC2026/2076
FLGA
ENA
CHARGE
PUMP
FLAG
RESPONSE
DELAY
GATE
CONTROL
CURRENT
LIMIT
OUTA
ENB
OSC.
CHARGE
PUMP
THERMAL
SHUTDOWN
UVLO
1.2V
REFERENCE
GATE
CONTROL
CURRENT
LIMIT
FLAG
RESPONSE
DELAY
MIC2026/2076
GND
MIC2026/2076 Block Diagram
IN
OUTB
FLGB
Functional Description
Input and Output
IN is the power supply connection to the logic circuitry
and the drain of the output MOSFET. OUT is the source
of the output MOSFET. In a typical circuit, current flows
from IN to OUT toward the load. If VOUT is greater than
V_IN, current will flow from OUT to IN, since the switch is
bidirectional when enabled. The output MOSFET and
driver circuitry are also designed to allow the MOSFET
source to be externally forced to a higher voltage than
the drain (V_OUT > V_IN) when the switch is disabled. In this
situation, the MIC2026/76 prevents undesirable current
flow from OUT to IN.
Thermal Shutdown
Thermal shutdown is employed to protect the device
from damage should the die temperature exceed safe
margins due mainly to short circuit faults. Each channel
employs its own thermal sensor. Thermal shutdown
shuts off the output MOSFET and asserts the FLG
output if the die temperature reaches 140°C and the
overheated channel is in current limit. The other channel
is not affected. If however, the die temperature exceeds
160°C, both channels will be shut off. Upon determining
a thermal shutdown condition, the MIC2076 will latch the
output off. In this case, a pull-up current source is
activated. This allows the output latch to automatically
reset when the load (such as a USB device) is removed.
The output can also be reset by toggling EN. Refer to
Figure 1 for timing details.
The MIC2026 will automatically reset its output when the
die temperature cools down to 120°C. The MIC2026
output and FLG signal will continue to cycle on and off
until the device is disabled or the fault is removed.
Figure 2 depicts typical timing.
Depending on PCB layout, package, ambient
temperature, etc., it may take several hundred
milliseconds from the incidence of the fault to the output
MOSFET being shut off. This time will be shortest in the
case of a dead short on the output.
Power Dissipation
The device’s junction temperature depends on several
factors such as the load, PCB layout, ambient
temperature, and package type. Equations that can be
used to calculate power dissipation of each channel and
junction temperature are found below:
P_D = R_DS(on) × I_OUT2
Total power dissipation of the device will be the
summation of P_D for both channels. To relate this to
junction temperature, the following equation can be
used:
June 2010
11
M9999-060410-B