View MIC5020_154986.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

MIC5020
Micrel
MIC5020
Current-Sensing Low-Side MOSFET Driver
General Description
The MIC5020 low-side MOSFET driver is designed to operate at frequencies greater than 100kHz (5kHz PWM for 2% to 100% duty cycle) and is an ideal choice for high-speed applications such as motor control, SMPS (switch mode power supplies), and applications using IGBTs. The MIC5020 can also operate as a circuit breaker with or without automatic retry. The MIC5020's maximum supply voltage lends itself to control applications using up to 50V. The MIC5020 can control MOSFETs that switch voltages greater than 50V. A rising or falling edge on the input results in a current source or sink pulse on the gate output. This output current pulse can turn on or off a 2000pF MOSFET in approximately 175ns. The MIC5020 then supplies a limited current (< 2mA), if necessary, to maintain the output state. An overcurrent comparator with a trip voltage of 50mV makes the MIC5020 ideal for use with a current sensing MOSFET. An external low value resistor may be used instead of a sensing MOSFET for more precise overcurrent control. An optional external capacitor connected to the CT pin may be used to control the current shutdown duty cycle from 20% to < 1%. A duty cycle from 20% to about 75% is possible with an optional pull-up resistor from CT to VDD. An open collector output provides a fault indication when the sense inputs are tripped. The MIC5020 is available in 8-pin SOIC and plastic DIP packages. Other members of the MIC502x series include the MIC5021 high-side driver and the MIC5022 half-bridge driver with a cross-conduction interlock.
Features
* * * * * * * * * * * * * 11V to 50V operation 175ns rise/fall time driving 2000pF TTL compatible input with internal pull-down resistor Overcurrent limit Fault output indication Gate to source protection Compatible with current sensing MOSFETs Lamp control Heater control Motor control Solenoid switching Switch-mode power supplies Circuit breaker
Applications
Ordering Information
Part Number MIC5020BM MIC5020BN Temperature Range -40C to +85C -40C to +85C Package 8-pin SOIC 8-pin Plastic DIP
Typical Application
V+
+11V to +50V 10F 150kHz max.
1 2 3 4
MIC5020 VDD Gate
8 7 6 5
Load
N-Channel Power MOSFET
Input Sense- Fault Sense+ CT Gnd
RSENSE = 50mV I TRIP RSENSE * increases time before retry
optional*
Low-Side Driver with Overcurrent Trip and Retry 5-162 October 1998
MIC5020
Micrel
Pin Configuration
1 VDD Gate 8 1 2 3 4 VDD Gate 8
2 Input Sense- 7 3 Fault Sense+ 6 4 CT Gnd 5
Input Sense- 7 Fault Sense+ 6 CT Gnd 5
DIP Package (N)
SOIC Package (M)
Block Diagram
6V Internal Regulator I1 CINT 2I1
Fault
CT
Normal
Fault Q1
Sense + Sense - 50mV ONESHOT
ON OFF
VDD
6V Gate
Input
10I2
I2
5
Transistor Count: 82
Pin Description
Pin Number 1 2 3 Pin Name VDD Input Fault Pin Function Supply: +11V to +50V. Decouple with 10F capacitor. TTL Compatible Input: Logic high turns the external MOSFET on. An internal pull-down returns an open pin to logic low. Overcurrent Fault Indicator: When the sense voltage exceeds threshold, open collector output is open circuit for 5s (tG(ON)), then pulled low for tG(OFF). tG(OFF) is adjustable from CT. Retry Timing Capacitor: Controls the off time (tG(OFF)) of the overcurrent retry cycle. (Duty cycle adjustment.) * Open = 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 RSENSE sets the load overcurrent trip point. Current Sense Comparator (-) Input: Connect to the low side of the sense resistor (usually power ground). Gate Drive: Drives the gate of an external power MOSFET. Also limits VGS to 15V max. to prevent Gate to Source damage. Will sink and source current.
4
CT
5 6
Gnd Sense +
7 8
Sense - Gate
October 1998
5-163
MIC5020
Micrel
Absolute Maximum Ratings
Supply Voltage (VDD) .................................................. +55V Input Voltage ................................................ -0.5V to +15V Sense Differential Voltage .......................................... 6.5V Sense + or Sense - to Gnd .......................... -0.5V to +50V Fault Voltage ............................................................... +50V Current into Fault ....................................................... 50mA Timer Voltage (CT) ..................................................... +5.5V
Operating Ratings
Supply Voltage (VDD) .................................... +11V to +50V Temperature Range SOIC ...................................................... -40C to +85C Plastic DIP .............................................. -40C to +85C
Electrical Characteristics
TA = 25C, Gnd = 0V, VDD = 12V, Sense +,- = 0V, Fault = Open, CT = Open, Gate CL = 1500pF unless otherwise specificed Symbol Parameter D.C. Supply Current Condition VDD = 12V, Input = 0V VDD = 50V, Input = 0V VDD = 12V, Input = 5V VDD = 50V, Input = 5V Input Threshold Input Hysteresis Input Pull-Down Current Fault Output Saturation Voltage Fault Output Leakage Current Limit Threshold Gate On Voltage Input = 5V Fault Current = 1.6mA Note 1 Fault = 50V Note 2 VDD = 12V VDD = 50V tG(ON) tG(OFF) tDLH tR tDLH tF fmax
Note 1 Note 2 Note 3 Note 4 Note 5 Note 6 Note 7
Min
Typ 0.8 2 0.8 4
Max 2 10 2 25 2.0
Units mA mA mA mA V V A V A mV V
0.8
1.4 0.1
10
20 0.15
40 0.4 +1 70
-1 30 10 14 2 10
0.01 50 11 15 5 20 400 700 900 500
18 10 50 800 1500 1500 1500
V s s ns ns ns ns kHz
Gate On Time, Fixed Gate Off Time, Adjustable Gate Turn-On Delay Gate Rise Time Gate Turn-Off Delay Gate Fall Time Maximum Operating Frequency
Voltage remains low for time affected by CT.
Sense Differential > 70mV Sense Differential > 70mV, CT = 0pF Note 3 Note 4 Note 5 Note 6 Note 7
100
150
When using sense MOSFETs, it is recommended that RSENSE < 50. Higher values may affect the sense MOSFET's current transfer ratio. Input switched from 0.8V (TTL low) to 2.0V (TTL high), time for Gate transition from 0V to 2V. Input switched from 0.8V (TTL low) to 2.0V (TTL high), time for Gate transition from 2V to 10V. Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 11V (Gate ON voltage) to 10V. Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 10V from 2V. Frequency where gate on voltage reduces to 10V with 50% input duty cycle.
5-164
October 1998
MIC5020
Micrel
Typical Characteristics
Supply Current vs. Supply Voltage
900
VIN = 5V 3.0
ISUPPLY (mA)
3.5
Turn-On Time vs. Supply Voltage
VGATE = 4V CL = 1500pF VIN = 0 to 5V Sq. Wave
1200 1100
tOFF (ns)
Turn-Off Time vs. Supply Voltage
800
tON (nS)
2.5
700 600 500
INCLUDES PROPAGATION DELAY
1000 900 800
2.0 1.5 1.0 0.5 VIN = 0V
VGATE = 4V CL = 1500pF VIN = 0 to 5V Sq. Wave
INCLUDES PROPAGATION DELAY
5 10 15 20 25 30 35 40 45 50 VSUPPLY (V)
400
700
5 10 15 20 25 30 35 40 45 50 VSUPPLY (V)
5
10
15 20 VSUPPLY (V)
25
30
100 80
IIN (A)
Input Current vs. Input Voltage
VSUPPLY = 12V
1200 1000
Turn-On Time vs. Gate Capacitance
25.0
Shutdown Duty Cycle (%)
VGATE = 4V
Overcurrent Shutdown Retry Duty Cycle
tON = 5s VSUPPLY = 12V
20.0 15.0 10.0 5.0 0.0 0.1
60 40 20 0
tON (ns)
800 600 400
INCLUDES PROPAGATION DELAY
0
5
10 15 VIN (V)
20
25
200 1x102
1x103 1x104 CGATE (pF)
1x105
1
10 100 CT (pF)
1000 10000
5
Sense Threshold vs. Temperature
80 70 VOLTAGE (mV) 60 50 40
Input Gate Sense +, - Differential Fault
TTL (H) 0V 15V (max.) 0V 50mV 0V Off On
30 20 -60 -30 0 30 60 90 120 150 TEMPERATURE (C)
Timing Diagram 1. Normal Operation
5s
20s
5s
Input Gate Sense +, - Differential Fault
TTL (H) 0V 15V (max.) 0V 50mV 0V Off On
Input Gate Sense +, - Differential Fault
TTL (H) 0V 15V (max.) 0V 50mV 0V Off On
Timing Diagram 2. Fault Condition, CT = Open October 1998 5-165
Timing Diagram 3. Fault Condition, CT = Grounded
MIC5020
Micrel
Functional Description
Refer to the MIC5020 block diagram. Input A signal greater than 1.4V (nominal) applied to the MIC5020 INPUT causes gate enhancement on an external MOSFET turning the external MOSFET on. An internal pull-down resistor insures that an open INPUT remains low, keeping the external MOSFET turned off. Gate Output Rapid rise and fall times on the GATE output are possible because each input state change triggers a one-shot which activates a high-value current sink (10I2) for a short time. This draws a high current through a current mirror circuit causing the output transistors to quickly charge or discharge the external MOSFET's gate. A second current sink continuously draws the lower value of current used to maintain the gate voltage for the selected state. An internal 15V Zener diode protects the external MOSFET by limiting the gate output voltage when VDD is connected to higher voltages. Overcurrent Limiting Current source I1 charges CINT upon power up. An optional external capacitor connected to CT is discharged through MOSFET Q1. A fault condition (> 50mV from SENSE + to SENSE -) causes the overcurrent comparator to enable current sink 2I1 which overcomes current source I1 to discharge CINT in a short time. When CINT is discharged, the INPUT is disabled, which turns off the GATE output; the FAULT output is enabled; and CINT and CT are ready to be charged. When the GATE output turns the MOSFET off, the overcurrent signal is removed from the sense inputs which deactivates current sink 2I1. This allows CINT and the optional capacitor connected to CT to recharge. A Schmitt trigger delays the retry while the capacitor(s) recharge. Retry delay is increased by connecting a capacitor to CT (optional). The retry cycle will continue until the the fault is removed or the input is changed to TTL low. If CT is connected to ground, the circuit will not retry upon a fault condition. Fault Output The FAULT output is an open collector transistor. FAULT is active at approximately the same time the output is disabled by a fault condition (5s after an overcurrent condition is sensed). The FAULT output is open circuit (off) during each successive retry (5s).
Applications Information
The MIC5020 MOSFET driver is intended for low-side switching applications where higher supply voltage, overcurrent sensing, and moderate speed are required. Supply Voltage A feature of the MIC5020 is that its supply voltage rating of up to 50V is higher than many other low-side drivers. The minimum supply voltage required to fully enhance an Nchannel MOSFET is 11V. A lower supply voltage may be used with logic level MOSFETs. Approximately 6V is needed to provide 5V of gate enhancement. Low-Side Switch Circuit Advantages A moderate-speed low-side driver is generally much faster than a comparable high-side driver. The MIC5020 can provide the gate drive switching times and low propagation delay times that are necessary for high-frequency highefficiency circuit operation in PWM (pulse width modulation) designs used for motor control, SMPS (switch mode power supply) and heating element control. Switched loads (on/off) can benefit from the MIC5020's fast switching times by allowing use of MOSFETs with smaller safe operating areas. (Larger MOSFETs are often required when using slower drivers.) Overcurrent Limiting A 50mV comparator is provided for current sensing. The low level trip point minimizes I2R losses when power resistors are used for current sensing. Flexibility in choosing drain or source side sensing is provided by access to both SENSE + and SENSE - comparator inputs. The adjustable retry feature can be used to handle loads with high initial currents, such as lamps, motors, or heating elements and can be adjusted from the CT connection. CT to ground causes maintained gate drive shutdown following overcurrent detection. CT open, or through a capacitor to ground, causes automatic retry . The default duty cycle (CT open) is approximately 20%. Refer to the electrical characteristics when selecting a capacitor for a reduced duty cycle. CT through a pull-up resistor to VDD increases the duty cycle. Increasing the duty cycle increases the power dissipation in the load and MOSFET. Circuits may become unstable at a duty cycles of about 75% or higher, depending on the conditions. Caution: The MIC5020 may be damaged if the voltage on CT exceeds the absolute maximum rating. An overcurrent condition is externally signaled by an open collector (FAULT) output. The MIC5020 may be used without current sensing by connecting SENSE + and SENSE - to ground. Current Sense Resistors Lead length can be significant when using low value (< 1) resistors for current sensing. Errors caused by lead length can be avoided by using four-terminal current sensing resistors. Four-terminal resistors are available from several manufacturers.
5-166
October 1998
MIC5020
Lamp Driver Application Incandescent lamps have a high inrush current (low resistance) when turned on. The MIC5020 can perform a "soft start" by pulsing the MOSFET (overcurrent condition) until the filament is warm enough for its current to decrease (resistance increases). The sense resistor is selected so the voltage across the sense resistor drops below the sense threshold (50mV) as the filament becomes warm. The MOSFET is no longer pulsed to limit current and the lamp turns completely on.
V+ (+11V to +12V)
Micrel
Current Sensing MOSFET Application A current sensing MOSFET allows current sensing without adding additional resistance to the power switching circuit. A current sensing MOSFET has two source connections: a "power source" for power switching and a "current source" for current sensing. The current from the current source is approximately proportional to the current through the power source, but much smaller. A current sensing ratio (ISOURCE/ ISENSE) is provided by the MOSFET manufacturer.
V+ (+13.2V, > 4.4A) Load +11V to +50V (+13.2V) 10F TTL Input (0V/5V) 1 2 3 4 MIC5020 VDD Gate 8 7 6 5 RSENSE (10) Input Sense- Fault Sense+ CT Gnd "( )" values apply to demo circuit. See text. (3, > 60W) N-Channel Current Sensing Power MOSFET (IRCZ24)
Incandescent Lamp (#1157) 10F TTL Input (0V/5V) 1 2 3 4 MIC5020 VDD Gate 8 7 6 5 RSENSE (0.041) N-Channel Power MOSFET (IRF540)
Input Sense- Fault Sense+ CT Gnd
"( )" values apply to demo circuit. See text.
Figure 1. Lamp Driver with Current Sensing A lamp may not fully turn on if the filament does not heat up adequately. Changing the duty cycle, sense resistor, or both to match the filament characteristics can correct the problem. Soft start can be demonstrated using a #1157 dual-filament automotive lamp. The value of RS shown in figure 1 allows for soft start of the higher-resistance filament (measures approx. 2.1 cold or 21 hot). Solenoid Driver Application The MIC5020 can be directly powered by the control voltage supply in typical 11Vdc through 50Vdc control applications. Current sensing has been omitted as an example.
V+
+11V to +50V MIC5020 VDD Gate
Solenoid
Diode
10F TTL Input
1 2 3 4
8 7 6 5
N-Channel Power MOSFET
Input Sense- Fault Sense+ CT Gnd
Figure 2. Solenoid Driver, Without Current Sensing A diode across the load protects the MOSFET from the voltage spike generated by the inductive load upon MOSFET turn off. The peak forward current rating of the diode should be greater than the load current. October 1998
Figure 3. Using a Current Sensing MOSFET The MOSFET current source is used to develop a voltage across a sense resistor. This voltage is monitored by the MIC5020 (SENSE + and SENSE - pins) to identify an overcurrent condition. The value of the sense resistor can be estimated with: RSENSE = (r VTRIP RDS(ON)) / (ILOAD RDS(ON) - VTRIP) where: RSENSE = external "sense" resistor VTRIP = 50mV (0.050V) for the MIC5020 r = manufacturer's current sense ratio: (ISOURCE/ISENSE) RDS(ON) = manufacturer's power source on resistance ILOAD = load current (power source current) The drain to source voltage under different fault conditions affects the behavior of the MOSFET current source; that is, the current source will respond differently to a slight overcurrent condition (VDS(ON) very small) than to a short circuit (where VDS(ON) is approximately equal to the supply voltage). Adjustment of the sense resistor value by experiment starting from the above formula will provide the quickest selection of RSENSE. Refer to manufacture's data sheets and application notes for detailed information on current sensing MOSFET characteristics. Figure 3 includes values which can be used to demonstrate circuit operation. The IRCZ24 MOSFET has a typical sense ratio of 780 and a RDS(ON) of 0.10. A large 3 wirewound load resistor will cause inductive spikes which should be suppressed using a diode (using the same configuration as figure 2).
5
5-167
MIC5020
Faster MOSFET Switching The MIC5020's GATE current can be multiplied using a pair of bipolar transistors to permit faster charging and discharging of the external MOSFET's gate.
+40V max.
Micrel
For test purposes, a 680 load resistor and 3 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 MIC5020AJB (extended temperature range version--no longer available) approaches -55C, the driver's off-state, gate-output offset from ground increases. If the operating environment of the MIC5020AJB includes low temperatures (-40C to -55C), add an external 2.2M resistor as shown in Figures 6a or 6b. 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.
V+
2N3904 +11V to +50V 10F 150kHz max. 1 2 3 4 MIC5020 VDD Gate 8 7 6 5 2N3906 N-Channel Power MOSFET (IRF540)
Input Sense- Fault Sense+ CT Gnd
Load
+11V to +50V
MIC5020 1 2 3 4 VDD Input Fault CT Gate Sense Sense Gnd 8 7 6 5 RSENSE 2.2M
Figure 4. Faster MOSFET Switching Circuit NPN and PNP transistors are used to respectively charge and discharge the MOSFET gate. The MIC5020 gate current is multiplied by the transistor . The switched circuit voltage can be increased above 40V by selecting transistors with higher ratings. Remote Overcurrent Limiting Reset In circuit breaker applications where the MIC5020 maintains an off condition after an overcurrent condition is sensed, the CT pin can be used to reset the MIC5020.
V+
10F
Figure 6a. Gate-to-Source Pull Down The gate-to-source configuration (refer to Figure 6a) is appropriate for resistive and inductive loads. This also causes the smallest decrease in gate output voltage.
V+
Load
+11V to +50V 10F TTL input
Retry (H) Maintained (L)
1 2 3
MIC5020 VDD Gate
8 7 6 5
N-Channel Power MOSFET
+11V to +50V 10F
MIC5020 1 2 3 4 VDD Input Fault CT Gate Sense Sense Gnd 8 7 6 5 2.2M RSENSE
Input Sense- Fault Sense+ CT Gnd
10k to 100k
4
Q1 2N3904
RSENSE
74HC04 (example)
Figure 5. Remote Control Circuit Switching Q1 on pulls CT low which keeps the MIC5020 GATE output off when an overcurrent is sensed. Switching Q1 off causes CT to appear open. The MIC5020 retries in about 20s and continues to retry until the overcurrent condition is removed.
Figure 6b. Gate-to-Ground Pull Down The gate-to-ground configuration (refer to Figure 6b) is appropriate for resistive, inductive, or capacitive loads. This configuration will decrease the gate output voltage slightly more than the circuit shown in Figure 6a.
5-168
October 1998
Load
Load

▲Up To Search▲

Price & Availability of MIC5020

	To Download MIC5020 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .