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PDF LT1158 Data sheet ( Hoja de datos )
| Número de pieza | LT1158 | |
| Descripción | Half Bridge N-Channel Power MOSFET Driver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LT1158
Half Bridge N-Channel
Power MOSFET Driver
FEATURES
n Drives Gate of Top Side MOSFET Above V+
n Operates at Supply Voltages from 5V to 30V
n 150ns Transition Times Driving 3000pF
n Over 500mA Peak Driver Current
n Adaptive Non-Overlap Gate Drives
n Continuous Current Limit Protection
n Auto Shutdown and Retry Capability
n Internal Charge Pump for DC Operation
n Built-In Gate Voltage Protection
n Compatible with Current-Sensing MOSFETs
n TTL/CMOS Input Levels
n Fault Output Indication
APPLICATIONS
n PWM of High Current Inductive Loads
n Half Bridge and Full Bridge Motor Control
n Synchronous Step-Down Switching Regulators
n Three-Phase Brushless Motor Drive
n High Current Transducer Drivers
n Battery-Operated Logic-Level MOSFETs
DESCRIPTION
A single input pin on the LT®1158 synchronously controls
two N-channel power MOSFETs in a totem pole configura-
tion. Unique adaptive protection against shoot-through
currents eliminates all matching requirements for the two
MOSFETs. This greatly eases the design of high efficiency
motor control and switching regulator systems.
A continuous current limit loop in the LT1158 regulates
short-circuit current in the top power MOSFET. Higher
start-up currents are allowed as long as the MOSFET VDS
does not exceed 1.2V. By returning the FAULT output to
the enable input, the LT1158 will automatically shut down
in the event of a fault and retry when an internal pull-up
current has recharged the enable capacitor.
An on-chip charge pump is switched in when needed to
turn on the top N-channel MOSFET continuously. Special
circuitry ensures that the top side gate drive is safely
maintained in the transition between PWM and DC opera-
tion. The gate-to-source voltages are internally limited to
14.5V when operating at higher supply voltages.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5365118.
TYPICAL APPLICATION
1N4148
PWM
0Hz TO
100kHz
+
10μF
+
1μF
0.01μF
BOOST DR
V+
V+
BOOST
T GATE DR
T GATE FB
T SOURCE
INPUT
SENSE+
LT1158
ENABLE
SENSE–
FAULT
B GATE DR
BIAS
B GATE FB
GND
24V
0.1μF
IRFZ34
+
500μF
LOW
ESR
+
RSENSE
0.015Ω
–
LOAD
IRFZ34
Top and Bottom Gate Waveforms
VIN = 24V
RL = 12Ω
1158 TA02
LT1158 TA01
1158fb
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
Current Limit Inhibit
VDS Threshold
1.50
1.45 V2 – V11
1.40
1.35
1.30
–40°C
1.25
+25°C
1.20 +85°C
1.15
1.10
1.05
1.00
0 5 10 15 20 25 30 35 40
SUPPLY VOLTAGE (V)
LT1158 G10
Bottom Gate Rise Time
400
350
300
250 CGATE = 10000pF
200
150 CGATE = 3000pF
100
50 CGATE = 1000pF
0
0 5 10 15 20 25 30 35 40
SUPPLY VOLTAGE (V)
LT1158 G11
LT1158
Bottom Gate Fall Time
400
350
300 CGATE = 10000pF
250
200
150 CGATE = 3000pF
100
50 CGATE = 1000pF
0
0 5 10 15 20 25 30 35 40
SUPPLY VOLTAGE (V)
LT1158 G12
Top Gate Rise Time
400
350
300 CGATE = 10000pF
250
200
CGATE = 3000pF
150
100
CGATE = 1000pF
50
0
0 5 10 15 20 25 30 35 40
SUPPLY VOLTAGE (V)
LT1158 G13
Top Gate Fall Time
400
350
300 CGATE = 10000pF
250
200
150 CGATE = 3000pF
100
CGATE = 1000pF
50
0
0 5 10 15 20 25 30 35 40
SUPPLY VOLTAGE (V)
LT1158 G14
Transition Times vs RGate
800
V+ = 12V
700 CGATE = 3000pF
600
500
RISE TIME
400
FALL TIME
300
200
100
0
0 10 20 30 40 50 60 70 80 90 100
GATE RESISTANCE (Ω)
LT1158 G15
1158fb
5
5 Page 
LT1158
APPLICATIONS INFORMATION
Ugly Transient Issues
In PWM applications the drain current of the top MOSFET
is a square wave at the input frequency and duty cycle.
To prevent large voltage transients at the top drain, a low
ESR electrolytic capacitor must be used and returned to
the power ground. The capacitor is generally in the range
of 250μF to 5000μF and must be physically sized for
the RMS current flowing in the drain to prevent heating
and premature failure. In addition, the LT1158 requires a
separate 10μF capacitor connected closely between pins
2 and 7.
The LT1158 top source and sense pins are internally
protected against transients below ground and above
supply. However, the gate drive pins cannot be forced
below ground. In most applications, negative transients
coupled from the source to the gate of the top MOSFET
do not cause any problems. However, in some high cur-
rent (10A and above) motor control applications, negative
transients on the top gate drive may cause early tripping
of the current limit. A small Schottky diode (BAT85) from
pin 15 to ground avoids this problem.
Switching Regulator Applications
The LT1158 is ideal as a synchronous switch driver to
improve the efficiency of step-down (buck) switching
regulators. Most step-down regulators use a high current
Schottky diode to conduct the inductor current when the
switch is off. The fractions of the oscillator period that the
switch is on (switch conducting) and off (diode conduct-
ing) are given by:
SWITCH
“ON” =
⎛
⎝⎜
VOUT
VIN
⎞
⎠⎟
•
TOTAL
PERIOD
SWITCH
“OFF”
=
⎛
⎝⎜
VIN
− VOUT
VIN
⎞
⎠⎟
•
TOTAL
PERIOD
Note that for VIN > 2VOUT, the switch is off longer than it
is on, making the diode losses more significant than the
switch. The worst case for the diode is during a short cir-
cuit, when VOUT approaches zero and the diode conducts
the short-circuit current almost continuosly.
Figure 3 shows the LT1158 used to synchronously drive a
pair of power MOSFETs in a step-down regulator applica-
tion, where the top MOSFET is the switch and the bottom
MOSFET replaces the Schottky diode. Since both conduc-
tion paths have low losses, this approach can result in very
high efficiency—from 90% to 95% in most applications.
And for regulators under 5A, using low RDS(ON) N-channel
MOSFETs eliminates the need for heatsinks.
T GATE DR
T GATE FB
T SOURCE
LT1158 SENSE+
VIN
+
RGS
RSENSE
+
VOUT
REF
PWM
FAULT
INPUT
SENSE–
B GATE DR
B GATE FB
1158 F03
Figure 3. Adding Synchronous Switching to a Step-Down Switching Regulator
1158fb
11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet LT1158.PDF ] | |
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