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参数资料
| 型号： | L497B |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 模拟信号调理 |
| 英文描述： | SPECIALTY ANALOG CIRCUIT, PDIP16 |
| 封装： | DIP-16 |
| 文件页数： | 8/11页 |
| 文件大小： | 474K |
| 代理商： | L497B |
Obsolete
Product(s)
- Obsolete
Product(s)
DWELL ANGLE CONTROL
The dwell angle control circuit calculates the con-
duction time D for the output transistor in relation to
the speed of rotation, to the supply voltage and to
the characteristics of the coil.
On the negative edge of the Hall-effect input signal
the capacitor CW begins discharging with a constant
current l11D. When the set peak value of the coil cur-
rent is reached, this capacitor charges with a con-
stant current I11C = 13.3 x I11D, and the coil current
is kept constant by desaturation of the driven stage
and the external darlington.
The capacitor CT starts charging on the posi-
tive.edge of the Hall-effect input signal with a con-
stant current I10C. The dwell angle, and conse-
quently the starting point of the coil current conduc-
tion, is decided by the comparison between V10 and
V11.
A positive hysteresis is added to the dwell compa-
rator to avoid spurious effects and CT is rapidly dis-
charged on the negative edge of Hall-effects input
signal.
In this way the average voltage on CW increases if
the motor speed decreases and viceversa in order
to maintain constant the ratio
td
T
at any motor speed.
td
T
is kept constant (and not
D
T
= cost) to control
the power dissipation and to have sufficient time to
avoid low energy sparks during acceleration.
DESATURATION TIMES IN STATIC
CONDITIONS
In static conditions and if CT = CW as recommended
and if the values of the application circuit of fig.4 are
used.
td
T
=
1
+ I11C / I11D
DESATURATION TIMES IN LOW AND HIGH
FREQUENCY OPERATION
Due to the upper limit of the voltage range of pin 11,
if the components of fig.4 are used, below 10 Hz
(300 RPM for a 4 cylinder engine) the OFF time
reaches its maximum value (about 50 ms) and then
the circuit gradually loses control of the dwell angle
because D = T – 50 ms.
Over 200 Hz (6000 RPM for a 4 cylinder engine) the
available time for the conduction is less than 3.5 ms.
If the used coil is 6 mH, 6A, the OFF time is reduced
to zero and the circuit loses the dwell angle control.
TRANSIENT RESPONSE
The ignition system must deliver constant energy
even during the condition of acceleration and decel-
eration of the motor below 80Hz/s. These conditions
can be simulated by means of a signal gene-rator
with a linearly modulated frequency between 1 Hz
and 200 Hz (this corresponds to a change between
30 and 6000 RPM for a 4 cylinders engine).
CURRENT LIMIT
The current in the coil is monitored by measuring the
Isense current flowing in the sensing resistor Rs on
the emitter of the external darlington. Isense is given
by :
Isense = Icoil + I14
When the voltage drop across Rs reaches the inter-
nal comparator threshold value the feedback loop is
activated and Isense kept constant (fig.1) forcing the
external darlington in the active region. In this con-
dition :
Isense = Icoil
When a precise peak coil current is required Rs must
be trimmed or an auxiliary resistor divider (R10, R11)
added :
Ic peak
(A) =
0.320
RS
)
R10
R11
+ 1
SLOW RECOVERY CONTROL (fig. 2)
If Isense has not reached 94 % of the nominal value
just before the negative edge of the Hall-effect input
signal, the capacitor Csrc and CW are quickly dis-
charged as long as the pick-up signal is "low". At the
next positive transition of the input signal the load
current starts immediately, producing the maximum
achievable Tdesat; then the voltage on CSRC in-
creases linearly until the standby is reached. During
this recovery time the CSRC voltage is converted into
a current which, substrated from the charging cur-
rent of the dwell capacitor, produces a Tdesat modu-
lation. This means that the Tdesat decreases slowly
until its value reaches, after a time TSRC, the nominal
7% value.
The time TSRC is given by:
Trsc = 12.9 R7 CSRC (ms)
where R7 is the biasing resistor at pin 12 (in K
) and
Csrc the capacitor at pin 8 (in
F).
L497
6/11
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L497D1 | 功能描述:马达/运动/点火控制器和驱动器 Hall Effect Control RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube |
| L4981 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:L4981 功率因数校正集成电路 |
| L4981A | 功能描述:功率因数校正 IC Very High Power RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel |
| L4981A | 制造商:STMicroelectronics 功能描述:POWER FACTOR CORRECTOR 4981 DIP20 |
| L4981A_01 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:POWER FACTOR CORRECTOR |
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