- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄384595 > LM1949N (NATIONAL SEMICONDUCTOR CORP) LM1949 Injector Drive Controller PDF資料下載
參數(shù)資料
| 型號： | LM1949N |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 外設(shè)及接口 |
| 英文描述： | LM1949 Injector Drive Controller |
| 中文描述： | 0.022 A BUF OR INV BASED PRPHL DRVR, PDIP8 |
| 封裝： | MINI, PLASTIC, DIP-8 |
| 文件頁數(shù)： | 5/10頁 |
| 文件大?。?/td> | 214K |
| 代理商： | LM1949N |
Typical Performance Characteristics
(Continued)
Sense Input Hold Voltage
vs Junction Temperature
Normalized Timer Function
vs Junction Temperature
LM1949N Junction
Temperature Rise Above
Ambient vs Supply Voltage
TL/H/5062–5
Application Hints
The injector driver integrated circuits were designed to be
used in conjunction with an external controller. The LM1949
derives its input signal from either a control oriented proces-
sor (COPS
TM
), microprocessor, or some other system. This
input signal, in the form of a square wave with a variable
duty cycle and/or variable frequency, is applied to Pin 1. In
a typical system, input frequency is proportional to engine
RPM. Duty cycle is proportional to the engine load. The cir-
cuits discussed are suitable for use in either open or closed
loop systems. In closed loop systems, the engine exhaust is
monitored and the air-to-fuel mixture is varied (via the duty
cycle) to maintain a perfect, or stochiometric, ratio.
INJECTORS
Injectors and solenoids are available in a vast array of sizes
and characteristics. Therefore, it is necessary to be able to
design a drive system to suit each type of solenoid. The
purpose of this section is to enable any system designer to
use and modify the LM1949 and associated circuitry to
meet the system specifications.
Fuel injectors can usually be modeled by a simple RL circuit.
Figure 3 shows such a model for a typical fuel injector. In
actual operation, the value of L
1
will depend upon the status
of the solenoid. In other words, L
1
will change depending
TL/H/5062–6
FIGURE 3. Model of a Typical Fuel Injector
upon whether the solenoid is open or closed. This effect, if
pronounced enough, can be a valuable aid in determining
the current necessary to open a particular type of injector.
The change in inductance manifests itself as a breakpoint in
the initial rise of solenoid current. The waveforms on Page 2
at the sense input show this occurring at approximately 130
mV. Thus, the current necessary to overcome the constric-
tive forces of that particular injector is 1.3 amperes.
PEAK AND HOLD CURRENTS
The peak and hold currents are determined by the value of
the sense resistor R
S
. The driver IC, when initiated by a
logic 1 signal at Pin 1, initially drives Darlington transistor Q
1
into saturation. The injector current will rise exponentially
from zero at a rate dependent upon L
1
, R
1
, the battery volt-
age and the saturation voltage of Q
1
. The drop across the
sense resistor is created by the solenoid current, and when
this drop reaches the peak threshold level, typically 385 mV,
the IC is tripped from the peak state into the hold state. The
IC now behaves more as an op amp and drives Q
1
within a
closed loop system to maintain the hold reference voltage,
typically 94 mV, across R
S
. Once the injector current drops
from the peak level to the hold level, it remains there for the
duration of the input signal at Pin 1. This mode of operation
is preferable when working with solenoids, since the current
required to overcome kinetic and constriction forces is often
a factor of four or more times the current necessary to hold
the injector open. By holding the injector current at one
fourth of the peak current, power dissipation in the sole-
noids and Q
1
is reduced by at least the same factor.
In the circuit ofFigure 1, it was known that the type of injec-
tor shown opens when the current exceeds 1.3 amps and
closes when the current then falls below 0.3 amps. In order
to guarantee injector operation over the life and tempera-
ture range of the system, a peak current of approximately 4
amps was chosen. This led to a value of R
S
of 0.1
X
. Divid-
ing the peak and hold thresholds by this factor gives peak
and hold currents through the solenoid of 3.85 amps and
0.94 amps respectively.
Different types of solenoids may require different values of
current. The sense resistor R
S
may be changed accordingly.
An 8-amp peak injector would use R
S
equal to .05
X
, etc.
Note that for large currents above one amp, IR drops within
the component leads or printed circuit board may create
substantial errors unless appropriate care is taken. The
sense input and sense ground leads (Pins 4 and 5 respec-
tively), should be Kelvin connected to R
S
. High current
should not be allowed to flow through any part of these
traces or connections. An easy solution to this problem on
double-sided PC boards (without plated-through holes) is to
have the high current trace and sense trace attach to the
R
S
lead from opposite sides of the board.
TIMER FUNCTION
The purpose of the timer function is to limit the power dissi-
pated by the injector or solenoid under certain conditions.
Specifically, when the battery voltage is low due to engine
cranking, or just undercharged, there may not be sufficient
voltage available for the injector to achieve the peak cur-
rent. In theFigure 2 waveforms under the low battery condi-
tion, the injector current can be seen to be leveling out at 3
5
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM20123 | 3A, 1.5MHz PowerWise㈢ Synchronous Buck Regulator |
| LM20123MH | 3A, 1.5MHz PowerWise㈢ Synchronous Buck Regulator |
| LM20123MHE | 3A, 1.5MHz PowerWise㈢ Synchronous Buck Regulator |
| LM20123MHX | 3A, 1.5MHz PowerWise㈢ Synchronous Buck Regulator |
| LM20124 | 4A, 1MHz PowerWise㈢ Synchronous Buck Regulator |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM1949N/NOPB | 功能描述:開關(guān)變換器、穩(wěn)壓器與控制器 RoHS:否 制造商:Texas Instruments 輸出電壓:1.2 V to 10 V 輸出電流:300 mA 輸出功率: 輸入電壓:3 V to 17 V 開關(guān)頻率:1 MHz 工作溫度范圍: 安裝風格:SMD/SMT 封裝 / 箱體:WSON-8 封裝:Reel |
| LM1949N/NOPB | 制造商:Texas Instruments 功能描述:Power Driver IC |
| LM194C | 制造商:Texas Instruments 功能描述: |
| LM194H/883 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:LM194/LM394 Supermatch Pair |
| LM194H-MCP | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Texas Instruments 功能描述: |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。