OM9369CM datasheet(6/10 Pages) ETC

6 / 10 page

output

clears the internal PWM latch, which in turn

commands the Phase Outputs to chop. For voltage-

mode control systems, pin 10 may be connected to the

Oscillator Timing Input, pin 11.

OSCILLATOR TIMING INPUT (Pin 11) -- The Oscillator

Timing Input sets a fixed PWM chopping frequency by

means of an internal resistor (Rosc), whose value is set

to 75k

Ω, connected from pin 11 to the +5V Reference

Output, and an internal capacitor (Cosc), whose value

is 1800pF, connected from pin 11 to Ground. In custom

applications, the recommended range of values for

Rosc is 10k

Ω to 100kΩ, and for Cosc is 0.001uF to

0.01uF, and the maximum operating frequency should

be kept below 20kHz.

The approximate oscillator

frequency is:

fo =

(Rosc x Cosc)

[Hz]

The voltage waveform on pin 11 is a ramp whose

magnitude is approximately 1.2Vp-p, centered at

approximately 1.6Vdc. In addition to the voltage-mode

PWM control, pin 11 may be used for slope

compensation in current-mode control applications.

ISENSE (Pin 12) -- This pin is connected to the output

of the internal current-sense amplifier. It drives a peak-

current (cycle-by-cycle) comparator which controls

Phase Output chopping, and a fail-safe current

comparator which, in the event of an output overcurrent

condition, activates the soft-start feature and disables

the Phase Outputs until the overcurrent condition is

removed. The magnitude of the voltage appearing at pin

12 is dependent upon the voltages present at the

current-sense amplifier inputs, ISH and ISL:

V(Isense) = 2.5V + [2 x ABS (ISH - ISL)] [Volts]

CURRENT SENSE INPUTS (ISH, Pin 13; ISL, pin 14)

-- These inputs to the current-sense amplifier are

interchangeable and they can be used as differential

inputs. The differential voltage applied between pins 13

and 14 should be kept below +/-0.5Vdc to avoid

saturation.

QUAD SELECT INPUT (Pin 15) -- This input is used to

set the OM9369CM in a half control or full control

chopping regime. When driven with a logic low level, the

OM9369CM is in the half control mode, whereby only

the three lower (pull-down) power switches associated

with the Phase Outputs are allowed to chop. Alternately,

when driven with a logic high level, the OM9369CM is in

the full control mode, where all six power switches (pull-

up and pull-down) associated with the Phase Outputs

are chopped by the PWM. During motor braking,

changing the logic state of the Quad Select Input has no

effect on the operation of the OM9369CM.

PIN DESCRIPTIONS / FUNCTIONALITY

VCC (Pin 1) -- The Vcc Supply input provides bias

voltage to all of the internal control electronics within

the OM9369CM, and should be connected to a

nominal +15Vdc power source. High frequency

bypass capacitors (10uF polarized in parallel with

0.1uF ceramic are recommended) should be

connected as close as possible to pin 1 and Ground

(pin 20).

DELAY (Pin 2) -- This pin must be connected to the

Brake/Tach Timing Input pin (pin 17) to ensure that

the high-side bootstrap capacitors are charged

during initial startup.

ERROR AMPLIFIER

(EA1- Input, Pin 3; EA1+

Input, Pin 5; EA1 Output, Pin 9) -- The Error

Amplifier is an uncommitted LM158-type operational

amplifier, providing the user with many external

control loop compensation options. This amplifier is

compensated for unity gain stability, so it can be

used as a unity gain input buffer to the internal PWM

comparator when pin 3 is connected to pin 9. The

output of the Error Amplifier is internally connected

to the PWM comparator's "-" input, simplifying

external layout connections.

+5V REFERENCE OUTPUT (Pin 6) -- This output

provides a temperature-compensated, regulated

voltage reference for critical external loads. It is

recommended that this pin be used to power the

external Hall-effect motor position sensors. By

design, the +5V reference must be in regulation

before the remainder of the control circuitry is

activated. This feature allows the Hall-effect sensors

to become powered and enabled before any Phase

Output is enabled in the OM9369CM, preventing

damage

turn-on.

High-frequency

bypass

capacitors (10uF polarized in parallel with 0.1uF

ceramic are recommended) should be connected as

close as possible to pin 5 and Ground (pin 20).

SPARE AMPLIFIER

(EA2- Input, Pin 7;

EA2+

Input, Pin 4; EA2 Output, Pin 8) -- The Spare

Amplifier is an uncommitted LM158-type operational

amplifier, and in addition to the internal error

amplifier, provides the user with additional external

control loop compensation options. This amplifier is

also compensated for unity gain stability and it can

be used as a unity gain input buffer when pin 7 is

connected to pin 8. If the Spare Amplifier is unused,

pin 4 should be connected to Ground, and pin 7

should be connected to pin 8.

PWM INPUT (Pin 10) -- This pin is connected to the

"+" input of the internal PWM comparator. The PWM

2.1 - 6

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