Newsgroups: comp.robotics
Path: brunix!uunet!sequent!muncher.sequent.com!coryc
From: coryc@sequent.com (Cory Carpenter)
Subject: Re: Anyone familiar with the EGC1857 stepper-motor controller?
Message-ID: <1992Dec10.011947.21706@sequent.com>
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Organization: Sequent Computer Systems Inc.
References: <1992Dec2.225902.24048@sequent.com> <1992Dec4.124428.13667@phx.mcd.mot.com> <1992Dec5.221538.29054@sequent.com>
Date: Thu, 10 Dec 92 01:19:47 GMT
Lines: 171

For anyone who cares, here is some more extensive information on the
NTE1857 stepper-motor controller IC.  I finally received the data sheets
from NTE... about five days after I got it working by the
best-guess-and-apply-voltage method.  It's nice to have my guesses
confirmed though!  

Advance apologies for any typos... I'll claim 'em.

-coryc

--------------8<----------cut here------------8<------------cut here-----------

NTE1857 /  EGC1857  
IC-LINEAR, STEPPER-MOTOR DRIVER

Description:

The NTE1857 is designed to drive a two-phase stepper motor in the
bipolar mode.  The circuit includes four input sections, a logic
decoding/sequencing section, two driver-stages for the motor coils, and
an output to indicate the Phase A drive state.

Application Information:
------------------------

General
	
	The NTE1857 integrated circuit is designed to drive a stepper
	positioning motor in applications such as disk drives and
	robotics.  The outputs can provide up to 350mA to each of two
	coils of a two-phase motor.  The outputs change state with each
	low-to-high transition of the clock input, with the new output
	state depending on the previouws state, as well as the input
	conditions on pins 8, 9, and 10.

Outputs (pins 2, 3, 14, 15)

	The outputs (L1-L4) are high current outputs, which when
	connected to a two-phase motor, provide two full-bridge
	configurations.  The polarities applied to the motor coils
	depend on which transistor (QH or QL) of each output is on,
	which in turn depends on the inputes andd the decoding
	circuitry.  The maximum sink current available at the outputs is
	a function of the resistor connected between pin 6 and ground
	(see section on Bias/Set operation).  Whenever the outputs are
	to be in a high imperance state, both transistors (QH and QL) of
	of each output are off.

Vd (pin 1)

	This pin allows for provision of a current path for the motor
	coil current during switching.  In order to suppress back-EMF
	voltage spikes.  Pin 1 is normally connected to Vm (pin 16)
	through a diode (Zener or regular), a resistor, or directly.
	The peak instantaneous voltage at the outputs (pines 2, 3, 14,
	and 15) must not exceed Vm by more than 6 volts.  The voltage
	drop across the internal clamping diodes must be included in
	design.  Parasitic diodes across each QL or each output provide
	for a complete circuit path for the switched current.
____
Full/Half Step (pin 9)
	
	When this input is at a logical 0 (<0.8 volts), the outputs
	change a full step with each clock cycle, with the sequence
	direction depending on the CW/CCW input (pin 10).  There are
	four steps (Phase A, B, C, and D) for each complete cycle of the
	sequencing logic.  Current flows through both motor coils during
	each step.

	When taken to a locical 1 (> 2.0 volts), the outputs change a
	half step with each clock cycle, with the sequence direction
	depending on the CW/CCW input (pin 10).  Eight steps (Phases A-H) 
	result for each complete cycle of the sequencing logic.  Phases
	A, C, E, and G correspond in polarity to phases A, B, C, and D of 
	the full-step sequence.  Phases B, D, F, and H provide current
	to one motor coil, while de-energizing the other coil.  The
	condition of the outputs of the de-energized coil depends on the
	OIC input (pin 8).

OIC (pin 8)

	The output impedance control input determines the output
	impedance to the de-engergized coil when operating the half-step
	mode.  When the outputs are in Phase B, D, F, or H and this
	input is at a logical 0 (< 0.8 volts), the two outputs to the
	de-engergized coil are in a high-impedance condition.  QL and QH
	of both outputs are off.  When this input is at a logical 1 
	(> 2.0 volts), a low impedance path requires connecting pin 1 (Vd)
	to pin 16 (Vm) as described elsewhere in the data sheet.
____
Bias/Set (pin 6)

	This pin can be used for three functions:  a) determining the
	maximum output sink current;  b) setting the internal logic to a
	known state;  c) reducing power consumption.

	a) The maximum output sink current is determined by the base
	drive current supplied to the lower transistors (QLs) of each
	output, which is in turn a function of IBS.  The appropriate
	value of Ibs is determined by:  I   = I   X 0.86
					 BS    OD   	
	
	Where IBS is in microamps, and IOD is the motor current/coil in
	milliamps.



Pin Description:
----------------

  Name		Symbol	Pin	Description
  ----		------	---	-----------
  Power Supply	V	16	Power supply pin for both the logic
                 M              circuit and the motor coil current.  Voltage 
				is +7.2 to +16.5

  Ground	Gnd	4, 5, 	Ground pins for the logic ciruit and the
			12, 13	motor coil current.  The physical
				configuration of the pins aids in
				dissipating heat from the within the IC
				package.

  Clamp Diode	V	1	The pin is used to protect the outputs
  Voltage	 D		where large voltage spikes may occur as
		 		the motor coils are switched.  Typically
				a diode is connected between this pin
				and pin 16.

  Driver        L1, L2, 2, 3,   High current outputs for the motor
  Outputs       L3, L4  14, 15  coils.  L1 and L2 are connected to one
				coil, and L3 and L4 to the other.
  ____		_
  Bias/Set	B/S	6	This pin is typically 0.7 below Vm.  The
  				current out of this pin (through a resistor 
				to ground) determines the maximum output sink
				current.  If the pin is opened (IBS < 5.0 uA) 
				the outputs assume a high imperdance condition,
				while the internal logic presets to a Phase A 
				condition.

  Clock		Clk	7	The positive edge of the clock input
				switches the outputs to the next
				position.  This input has no effect if
				pin 6 is open.
  ____          _
  Full/Half 	F/HS    9	When low (logical 0), each clock pulse
  Step				will cause the motor to rotate one full
  				step.  When high, each clock pulse will
				cause the motor to rotate one-half step.
  _________     __
  Clockwise/	CW/CCW  10	This input allows reversing the
  Counterclockwise		rotation of the motor.

  Output 	OIC	8	This input is relevant only in the half
  Impedance			step mode (pin 9 > 2.0 volts).  When low,
  Control			(logical 0), the two driver outputs of
  				the non-engergized coil will be in a
				high impedance condition.  when high,
				the same driver outputs will be at a low
				impedance referenced to Vm.
  _______	____
  Phase A	Ph A	11	This open-collector output indicates
  				(when low) that the driver outputs are in the 
				Phase A condition (L1=L3=VOHD, L2=L4=VOLD).


-- 
|    >> Disclaimer: I speak for Sequent only in our hardware manuals <<       |
|Cory R. Carpenter, Tech Writer |"Verbosity leads to unclear, inarticulate... |
|Sequent Computer Systems, Inc. | things."       -- Vice President Dan Quayle |
|    coryc@sequent.com          |                                             |
