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參數(shù)資料
| 型號(hào)： | LMD18201 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 3A, 55V H-Bridge |
| 中文描述： | 第3A，55V的H橋 |
| 文件頁(yè)數(shù)： | 6/8頁(yè) |
| 文件大小： | 261K |
| 代理商： | LMD18201 |
Application Information
(Continued)
supply to ground. Typically the ceramic capacitor can be
eliminated in the presence of the voltage suppressor. Note
that when driving high load currents a greater amount of sup-
ply bypass capacitance (in general at least 100 μF per Amp
of load current) is required to absorb the recirculating cur-
rents of the inductive loads.
CURRENT LIMITING
Current limiting protection circuitry has been incorporated
into the design of the LMD18201. With any power device it is
important to consider the effects of the substantial surge cur-
rents through the device that may occur as a result of
shorted loads. The protection circuitry monitors the current
through the upper transistors and shuts off the power device
as quickly as possible in the event of an overload condition
(the threshold is set to approximately 10A). In a typical motor
driving application the most common overload faults are
caused by shorted motor windings and locked rotors. Under
these conditions the inductance of the motor (as well as any
series inductance in the V
supply line) serves to reduce
the magnitude of a current surge to a safe level for the
LMD18201. Once the device is shut down, the control cir-
cuitry will periodically try to turn the power device back on.
This feature allows the immediate return to normal operation
once the fault condition has been removed. While the fault
remains however, the device will cycle in and out of thermal
shutdown. This can create voltage transients on the V
supply line and therefore proper supply bypassing tech-
niques are required.
The most severe condition for any power device is a direct,
hard-wired (“screwdriver”) long term short from an output to
ground. This condition can generate a surge of current
through the power device on the order of 15 Amps and re-
quire the die and package to dissipate up to 500W of power
for the short time required for the protection circuitry to shut
off the power device. This energy can be destructive, particu-
larly at higher operating voltages (
>
30V) so some precau-
tions are in order. Proper heat sink design is essential and it
is normally necessary to heat sink the V
supply pin (pin 6)
with 1 square inch of copper on the PC board.
INTERNAL CHARGE PUMP AND USE OF
BOOTSTRAP CAPACITORS
To turn on the high-side (sourcing) DMOS power devices,
the gate of each device must be driven approximately 8V
more positive than the supply voltage. To achieve this an in-
ternal charge pump is used to provide the gate drive voltage.
As shown in (Figure 4), an internal capacitor is alternately
switched to ground and charged to about 14V, then switched
to V
thereby providing a gate drive voltage greater than V
S
.
This switching action is controlled by a continuously running
internal 300 kHz oscillator. The rise time of this drive voltage
is typically 20 μs which is suitable for operating frequencies
up to 1 kHz.
For higher switching frequencies, the LMD18201 provides
for the use of external bootstrap capacitors. The bootstrap
principle is in essence a second charge pump whereby a
large value capacitor is used which has enough energy to
quickly charge the parasitic gate input capacitance of the
power device resulting in much faster rise times. The switch-
ing action is accomplished by the power switches them-
selves (Figure 5). External 10 nF capacitors, connected from
the outputs to the bootstrap pins of each high-side switch
provide typically less than 100 ns rise times allowing switch-
ing frequencies up to 500 kHz.
INTERNAL PROTECTION DIODES
A major consideration when switching current through induc-
tive loads is protection of the switching power devices from
the large voltage transients that occur. Each of the four
switches in the LMD18201 have a built-in protection diode to
clamp transient voltages exceeding the positive supply or
ground to a safe diode voltage drop across the switch.
The reverse recovery characteristics of these diodes, once
the transient has subsided, is important. These diodes must
come out of conduction quickly and the power switches must
be able to conduct the additional reverse recovery current of
the diodes. The reverse recovery time of the diodes protect-
ing the sourcing power devices is typically only 70 ns with a
reverse recovery current of 1A when tested with a full 3A of
forward current through the diode. For the sinking devices
the recovery time is typically 100 ns with 4A of reverse cur-
rent under the same conditions.
DS010793-6
FIGURE 4. Internal Charge Pump Circuitry
DS010793-7
FIGURE 5. Bootstrap Circuitry
www.national.com
6
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LMD18201T | 3A, 55V H-Bridge |
| LMD18245 | 3A, 55V DMOS Full-Bridge Motor Driver |
| LMD18245T | 3A, 55V DMOS Full-Bridge Motor Driver |
| LMD18400 | Quad High Side Driver |
| LMD18400N | Quad High Side Driver |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMD18201T | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
| LMD18201T | 制造商:Texas Instruments 功能描述:HALF BRIDGE 3A 55V 18201 SIL-11 |
| LMD18201T/NOPB | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 3A 55V H-Bridge RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
| LMD18201T/NOPB | 制造商:Texas Instruments 功能描述:Motor Controller ICs |
| LMD18245 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3A, 55V DMOS Full-Bridge Motor Driver |
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