MIC2026(2000) 데이터 시트보기 (PDF) - Micrel
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MIC2026 Datasheet PDF : 16 Pages
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MIC2026/2076
Block Diagram
ENA
ENB
CHARGE
PUMP
OSC.
CHARGE
PUMP
MIC2026/2076
FLAG
RESPONSE
DELAY
GATE
CONTROL
CURRENT
LIMIT
THERMAL
SHUTDOWN
UVLO
1.2V
REFERENCE
GATE
CONTROL
CURRENT
LIMIT
FLAG
RESPONSE
DELAY
GND
FLGA
OUTA
IN
OUTB
FLGB
Micrel
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 VIN, 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 (VOUT > VIN) 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 effected. If however, the die tem-
perature 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 fac-
tors 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.
PD = RDS(on) × IOUT2
Total power dissipation of the device will be the summation of
PD for both channels. To relate this to junction temperature,
the following equation can be used:
TJ = PD × θJA + TA
where:
TJ = junction temperature
TA = ambient temperature
θJA = is the thermal resistance of the package
MIC2026/2076
10
March 2000
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