MIC5021
Micrel
Pin Configuration
1 V
DD
2 Input
3 C
T
4 Gnd
V
BOOST
8
Gate 7
Sense− 6
Sense+ 5
1
2
3
4
V
DD
Input
C
T
V
BOOST
8
Gate 7
Sense− 6
Gnd Sense+ 5
DIP Package
(N)
SOIC Package
(M)
Block Diagram
6V Internal Regulator
I
1
C
INT
2I
1
Fault
C
T
Normal
V
DD
CHARGE
PUMP
V
BOOST
Q1
Sense +
Sense –
ON
15V
50mV
OFF
Input
↑
ONE-
↓
SHOT
6V
Gate
10I
2
I
2
Transistor: 106
Pin Description
Pin Number
1
2
3
Pin Name
V
DD
Input
C
T
Pin Function
Supply: +12V to +36V. Decouple with
≥
10µF capacitor.
TTL Compatible Input: Logic high turns the external MOSFET on. An
internal pull-down returns an open pin to logic low.
Retry Timing Capacitor: Controls the off time (t
G(OFF)
) of the overcurrent
retry cycle. (Duty cycle adjustment.)
• Open = approx. 20% duty cycle.
• Capacitor to Ground = approx. 20% to < 1% duty cycle.
• Pull-up resistor = approx. 20% to approx. 75% duty cycle.
• Ground = maintained shutdown upon overcurrent condition.
Circuit Ground
Current Sense Comparator (+) Input: Connect to high side of sense resistor
or current sensing MOSFET sense lead. A built-in offset in conjunction with
R
SENSE
sets the load overcurrent trip point.
Current Sense Comparator (–) Input: Connect to the low side of the sense
resistor (usually the high side of the load).
Gate Drive: Drives the gate of an external power MOSFET. Also limits V
GS
to 15V max. to prevent Gate-to-Source damage. Will sink and source
current.
Charge Pump Boost Capacitor: A bootstrap capacitor from V
BOOST
to the
FET source pin supplies charge to quickly enhance the Gate output during
turn-on.
4
5
Gnd
Sense +
6
7
Sense –
Gate
8
V
BOOST
5-170
October 1998
MICREL [ MICREL SEMICONDUCTOR ]
