MIC5021 Micrel Semiconductor, MIC5021 Datasheet - Page 9

• Manufacturer Part Number: MIC5021
• Description: High-Speed High-Side MOSFET Driver
• Manufacturer: Micrel Semiconductor

Remote Overcurrent Limiting Reset
In circuit breaker applications where the MIC5021 maintains
an off condition after an overcurrent condition is sensed, the
C
Switching Q1 on pulls C
output off when an overcurrent is sensed. Switching Q1 off
causes C
20 s and continues to retry until the overcurrent condition is
removed.
For demonstration purposes, a 680
sense resistor will produce an overcurrent condition when the
load’s supply (V+) is approximately 12V or greater.
Low-Temperature Operation
As the temperature of the MIC5021AJB (extended tempera-
ture range version—no longer available) approaches –55 C,
the driver’s off-state, gate-output offset from ground in-
creases. If the operating environment of the MIC5021AJB
includes low temperatures (–40 C to –55 C), add an external
2.2M resistor as shown in Figures 12a or 12b. This assures
that the driver’s gate-to-source voltage is far below the
external MOSFET’s gate threshold voltage, forcing the
MOSFET fully off.
October 1998
MIC5021
T
pin can be used to reset the MIC5021.
Maintained (L)
Retry (H)
TTL Input
T
(example)
74HC04
Figure 11. Remote Control Circuit
to appear open. The MIC5021 retries in about
10k to
100k
10µF
2N3904
Q1
T
low which keeps the MIC5021
1
2
3
4
V
Input
C
Gnd
DD
T
MIC5021
Sense
Sense
V
BOOST
Gate
load resistor and 3
8
7
6
5
+12V to +20V
0.01
µF
N-Channel
Power
MOSFET
R
SENSE
GATE
5-177
The gate-to-source configuration (refer to Figure 12a) is
appropriate for resistive and inductive loads.
causes the smallest decrease in gate output voltage.
The gate-to-ground configuration (refer to Figure 12b) is
appropriate for resistive, inductive, or capacitive loads. This
configuration will decrease the gate output voltage slightly
more than the circuit shown in Figure 12a.
TTL Input
TTL Input
Figure 12b. Gate-to-Ground Pull Down
Figure 12a. Gate-to-Source Pull Down
10µF
10µF
1
2
3
4
V
Input
C
Gnd
1
2
3
4
–40 C to –55 C
MIC5021AJB
add resistor for
DD
T
V
Input
C
Gnd
–40 C to –55 C
MIC5021AJB
add resistor for
DD
T
operation
Sense
Sense
V
operation
BOOST
Sense
Sense
Gate
V
BOOST
Gate
8
7
6
5
8
7
6
5
2.7
nF
2.2M
+12V to +36V
2.2M
2.7
nF
+12V to +36V
R
This also
SENSE
R
SENSE
Micrel
5