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PDF UC3638 Data sheet ( Hoja de datos )
| Número de pieza | UC3638 | |
| Descripción | Advanced PWM Motor Controller | |
| Fabricantes | Unitrode | |
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Hay una vista previa y un enlace de descarga de UC3638 (archivo pdf) en la parte inferior de esta página. Total 9 Páginas | ||
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UC1638
UC2638
UC3638
Advanced PWM Motor Controller
FEATURES
• Single or Dual Supply Operation
• Accurate High Speed Oscillator
• Differential X5 Current Sense
Amplifier
• Bidirectional Pulse-by-Pulse
Current Limiting
• Programmable Oscillator
Amplitude and PWM Deadband
• Dual 500mA Totem Pole Output
Drivers
• Dual 60V, 50mA Open Collector
Drivers
• Undervoltage Lockout
BLOCK DIAGRAM
DESCRIPTION
The UC1638 family of integrated circuits are advanced pulse width modula-
tors intended for a variety of PWM motor drive and amplifier applications re-
quiring either uni-directional or bi-directional drive circuits. Similar in
architecture to the UC1637, all necessary circuitry is included to generate an
analog error signal and modulate two bi-directional pulse train outputs in pro-
portion to the error signal magnitude and polarity.
Key features of the UC1638 include a programmable high speed triangle os-
cillator, a 5X differential current sensing amplifier, a high slew rate error am-
plifier, high speed PWM comparators, and two 50mA open collector as well
as two ±500mA totem pole output stages. The individual circuit blocks are
designed to provide practical operation to switching frequencies of 500kHz.
Significant improvements in circuit speed, elimination of many external pro-
gramming components, and the inclusion of a differential current sense am-
plifier, allow this controller to be specified for higher performance
applications, yet maintain the flexibility of the UC1637. The current sense
amplifier in conjunction with the error amplifier can be configured for average
current feedback. The additional open collector outputs provide a drive signal
continued
1/98
UDG-95048-4
1 page  
PIN DESCRIPTIONS (cont.)
series with the source or emitter of the low side switch in
the full bridge develops the signal that is applied to this
pin. At differential inputs of ±500mV typical (referenced
to CS+)the controller reaches the current limit level,
which truncates the output pulse.
CS+: This is the non-inverting input to the X5 current
sense amplifier. The common mode input range for this
pin extends from VEE−1V to VCC−4V. The characteris-
tics for this pin are identical to CS-.
CSOUT: This is the output of the X5 current sense am-
plifier. Voltage levels greater than ±2.5V referenced to
AREF will cause the device to enter current limit. An in-
ternal 100 ohm resistor between the amplifier output
and CSOUT is provided to create a high frequency
noise filter with an external capacitor to VEE. When
used for average current feedback, CSOUT is summed
into INV.
CT: A capacitor from CT to VEE will set the triangle os-
cillator frequency according to the following equation:
F= 1
5 • RT • CT
The waveform on CT is symmetrical about the voltage
on AREF and is applied internally to the inputs of hte
PWM comparators. Use a high quality ceramic capacitor
with low ESL and ESR for best results. A minimum CT
value of 200 pF insures good accuracy and less suscep-
tibility to circuit layout parasitics. The oscilator and PWM
are designed to provide practical operation to 500kHz.
DB: This high impedance input programs output pulse
train deadtime. A stable DC voltage between 0V and
REF will set a bi-directional deadband centered about
the level on COMP. The deadband level is equal to: 5V −
VDB. That is, 1V on DB will program ±4V of deadband
centered about the COMP pin level. A convenient
method for generating the programming level is a volt-
age divider tap off of REF.
INV: This is the inverting input to the Voltage amplifier.
The common mode input range for this pin extends from
VEE+2V to VCC−1V. It can be tied to a command signal
generated by a rate feedback element or to a position
control signal. In average current feedback applications,
this input is tied to the output of the X5 current sensing
amplifier (CSOUT).
PVE: This is the high current ground for the IC. The ex-
ternal MOSFET driver transistors are referenced to this
UC1638
UC2638
UC3638
ground. Internal level shifting circuitry gives the option of
tying this pin to VEE, or the system ground in split sup-
ply applications.
PVSET: A DC voltage on PVSET programs the upper
and lower thresholds for the oscillator by the following
relationship:
VPK − VVLY = 5 • VPVSET.
The input voltage range on PVSET is 0.5V to REF.
REF: REF is the output of the precision reference. The
output is capable of supplying 15mA to peripheral cir-
cuitry and is internally short circuit current limited. By-
pass REF to VEE with a 0.1µF ceramic capacitor for
best performance.
RT: A single resistor from RT to VEE sets the charging
and discharging currents for the triangle oscillator. The
actual charge and discharge is 2X the current pro-
grammed by RT and PVSET. For best performance the
current out of RT should be limited to 1mA. The voltage
level on the RT pin is a buffered version of the PVSET
pin voltage. Therefore, if the PVSET voltage divider is
tied between VCC and VEE to incorporate line feedfor-
ward, the triangle waveform frequency will remain con-
stant.
SD: A voltage on SD within 2.5V (typical) of VCC will
cause the UC3638 to enter a UVLO condition which dis-
ables all of the driver outputs. With an external voltage
divider across VCC and VEE, and a capacitor between
SD and VCC, a delayed turn-on characteristic can be
generated. Since the 2.5V threshold is temperature sta-
bilized it can also be used as a higher UVLO threshold
for applications which require a starting voltage higher
than the internal 9V UVLO threshold.
VEE: All voltages are measured with respect to this pin.
All bypass capacitors and timing components except
those listed under the PVE section should be connected
to this pin. Component leads should be as short and di-
rect as possible. VEE is generally connected to the most
negative voltage supply in the system. In single supply
applications, VEE is tied to the system ground.
VCC: Positive supply rail for the IC. Bypass this pin to
VEE and PVE with 0.1 to 1µF low ESL, ESR ceramic
capacitor(s). The maximum voltage for VCC is 40V ref-
erenced to VEE. The turn on voltage level on VCC is 9V
with 1V of hysteresis.
5
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet UC3638.PDF ] | |
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