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PDF BA6438S Data sheet ( Hoja de datos )
| Número de pieza | BA6438S | |
| Descripción | 3-phase motor driver | |
| Fabricantes | ROHM Semiconductor | |
| Logotipo |  |
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Motor driver ICs
3-phase motor driver
BA6438S
BA6438S
The BA6438S is a 3-phase, full-wave, pseudo-linear motor driver suited for VCR capstan motors. The IC has a torque
ripple cancellation circuit to reduce wow and flutter, and an output transistor saturation prevention circuit that provides
superb motor control over a wide range of current. The built-in motor power switching regulator allows applications with
low power consumption
!Applications
3-phase VCR capstan motors
!Features
1) 3-phase, full-wave, pseudo-linear drive system.
2) Torque ripple cancellation circuit.
3) Reversal brake based on the detection of motor
direction.
4) Output transistor (high-and low-sides) saturation
prevention circuit
5) Motor power switching regulator with oscillation circuit.
6) Output-to-GND short-circuit detection.
7) Available in SDIP 24-pin power package (with radiation
fins).
!Absolute maximum ratings (Ta = 25°C)
Parameter
Symbol
Limits
Applied voltage
VCC
7
Applied voltage
Power dissipation
VM
Pd
24
2000∗1
Operating temperature
Topr
−10 ∼ +75
Storage temperature
Tstg
−40 ∼ +150
Allowable output current
IOpeak
1.7∗2
∗1 Reduced by 16mW for each increase in Ta of 1°C over 25°C.
∗2 Should not exceed the ASO value.
Unit
V
V
mW
°C
°C
A
!Recommended operating conditions (Ta = 25°C)
Parameter
Operating power supply voltage
Operating power supply voltage
Symbol
VCC
VM
Min.
4
3
Typ.
5
12
Max.
6
23
Unit
V
V
1 page  
Motor driver ICs
(4) Motor direction control (pin 11)
The motor mode is :
Forward when the pin 11 voltage is less than 0.9V,
Stop when the voltage is between 1.3 ~ 3.0V,
Reverse when the voltage is above 3.5V.
In the stop mode, high-and low-side output transistors
are turned off, resulting in a high impedance state.
(5) Output transistor saturation prevention circuit
This circuit monitors the output voltage and maintain the
operation of the output transistors below their saturation
levels. Operating the transistors in the linear characteristic
range provides good control over a wide range of current
and good torque characteristics even during overloading.
0 800mA Output current
Output
saturation
voltage
1.5V
HIGH level voltage
Fig.5 High level output voltage vs.
output current (reference curves)
LOW level voltage
1.3V
Output saturation voltage
ATC-pin voltage
Output current
0 800mA
Fig.6 Low level output voltage vs. output
current (reference curves)
(6) Switching regulator
The BA6438S has a switching regulator output pin. The
IC outputs a PWM signal by comparing the output of the
internal oscillator with the HIGH level output voltage
monitored.
BA6438S
VM 24
+
HIGH level
voltage monitor
Oscillator
15
OSC
14 VS
13
REG
Fig. 7
As shown in Fig. 7, the switch regulator circuit reduces the
power consumed by the IC by reducing the collector-to-
emitter (C-E) voltage of the driver transistors.
Nearly all the power dissipated by the IC is dissipated be-
tween the collectors and emitters of the output transistors.
More power is consumed as the C-E voltage increases and
as the output current increases.
The output transistor C-E voltage is equal to the difference
between the supply voltage and the voltage applied to the
motor. Because the voltage across the motor decreases with
decreasing drive current, the C-E voltage must increase if the
supply voltage is fixed.
Therefore, to improve the efficiency of the driver and to
prevent the power rating of the IC being exceeded, the supply
voltage must be varied in response to changes in the output
current. The supply voltage is decreased at low current and
increased at high current so that no excessive voltage is
applied between the transistor collectors and emitters .
(7) Output-to-ground short-circuit detection
The motor output pins of the IC may be short-circuited to the
ground by some fault conditions. A short-circuited output can
destroy the output transistors because of excessive current,
excessive voltage, or both. Even when a short-circuit
condition does not completely destroy the device, it can still
cause extreme overheating. To prevent this, the BA6438S
contains a short-circuit detection circuit that turns off the motor
drive current if the output-to-ground potential becomes
abnormally low.
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet BA6438S.PDF ] | |
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