JRC NJU39612 User Manual

MICROSTEPPING MOTOR CONTROLLER WITH DUAL DAC

■ GENERAL DESCRIPTION ■ PACKAGE OUTLINE

NJU39612 is a dual 7-bit+sign; Digital-to-Analog Converter
(DAC) developed to be used in micro stepping applications
together with the dual stepper motor driver. The NJU39612
has a set of input registers connected to an 8-bit data port for
easy interfacing directly to a microprocessor. Two registers
are used to store the data for each seven-bit DAC, the eighth
bit being a sign bit (sign/magnitude coding).

NJU39612E2

■ FEATURES

• Analog control voltages from 3V down to 0.0V

• High-speed microprocessor interface

• Full -scale error ±1 LSB

NJU39612

• Fast conversion speed 3 µs

• Matches the dual stepper motor drivers

• Package EMP20

■ BLOCK DIAGRAM

WR

CS

A0

D7 - D0

RESET

POR

V

DD

E1

C

E2

C

R

DA- Data 1

E
D

R

DA- Data 2

E
D

R

V

Ref

NJU39612

D / A

D / A

Sign

DA

DA

Sign

1

1

2

2

Figure 1. Block Diagram

V

ss

■ PIN CONFIGURATION

V

DA

Sign

VDD

WR

1

ref

2

1

3

1

4
5

NJU39612E2

20
19

18
17

16

Reset

DA

2

Sign
V

ss

CS

NJU39612

2

6

D7

D6

7

D5

8

D4

9

10

D3 D2

15

14
13
12
11

NC
A0
D0
D1

Figure 2. Pin configuration

■ PIN DESCRIPTION

Refer to figure 2.

EMP Symbol Description

1V

Ref

2DA1Digital-to-Analog 1, voltage output. Output between 0.0 V and V
3 Sign

4V

DD

5 WR Write, TTL/CMOS level, input for writing to internal registers. Data is clocked into flip flops on positive

6 D7 Data 7, TTL/CMOS level, input to set data bit 7 in data word.
7 D6 Data 6, TTL/CMOS level, input to set data bit 6 in data word.
8 D5 Data 5, TTL/CMOS level, input to set data bit 5 in data word.
9 D4 Data 4, TTL/CMOS level, input to set data bit 4 in data word.
10 D3 Data 3, TTL/CMOS level, input to set data bit 3 in data word.
11 D2 Data 2, TTL/CMOS level, input to set data bit 2 in data word.
12 D1 Data 1, TTL/CMOS level, input to set data bit 1 in data word.
13 D0 Data 0, TTL/CMOS level, input to set data bit 0 in data word.
14 A0 Address 0, TTL/CMOS level, input to select data transfer, A0 selects between cannel 1 (A0 = LOW) and

15 NC Not connected
16 CS Chip Select, TTL/CMOS level, input to select chip and activate data transfer from data inputs. LOW level

17 V

SS

18 Sign

19 DA

2

20 Reset Reset, digital input resetting internal registers. HIGH level = Reset, V

Voltage reference supply pin, 2.5 V nominal (3.0 V maximum)

- 1 LSB.

ref

Sign 1, TTL/CMOS level. To be connected directly to NJM377x phase input. Databit D7 is transfered non

1

inverted from NJU39612 data input.
Voltage Drain-Drain, logic supply voltage. Normally +5 V.

edge.

channel 2 (A0 = HIGH).

= chip is selected.
Voltage Source-Source. Ground pin, 0 V reference for all signals and measurements unless otherwise

noted.
Sign 2. TTL/CMOS level. To be connected directly to NJM377x phase input. Data bit D7 is transfered

2

non-inverted from NJU39612 data input.
Digital-to-Analog 2, voltage output. Output between 0.0 V and V

- 1 LSB.

ref

≥ 3.5 V = HIGH level. Pulled low

Res

internally.

NJU39612

■ DEFINITION OF TERMS
Resolution

Resolution is defined as the reciprocal of the number of discrete steps in the DAC output. It is directly related to the
number of switches or bits within the DAC. For example, NJU39612 has 27, or 128, output levels and therefor has 7
bits resolution. Remember that this is not equal to the number of microsteps available.

Linearity Error

Linearity error is the maximum deviation from a straight line passing through the end points of the DAC transfer
characteristic. It is measured after adjusting for zero and full scale. Linearity error is a parameter intrinsic to the
device and cannot be externally adjusted.

Power Supply Sensitivity

Power supply sensitivity is a measure of the effect of power supply changes on the DAC full-scale output.

Settling Time

Full-scale current settling time requires zero-to-full-scale or full-scale-to-zero output change. Settling time is the
time required from a code transition until the DAC output reaches within ±1/2LSB of the final output value.

Full-scale Error

Full-scale error is a measure of the output error between an ideal DAC and the actual device output.

Differential Non-linearity

The difference between any two consecutive codes in the transfer curve from the theoretical 1LSB, is differential
non-linearity

Monotonic

If the output of a DAC increases for increasing digital input code, then the DAC is monotonic. A 7-bit DAC which is
monotonic to 7 bits simply means that increasing digital input codes will produce an increasing analog output.
NJU39612 is monotonic to 7 bits.

■ FUNCTIONAL DESCRIPTION

Each DAC channel contains one register and a D/A converter. A block diagram is shown on the first page.
The sign outputs generate the phase shifts, i.e., they reverse the current direction in the phase windings.

Data Bus Interface

NJU39612 is designed to be compatible with 8-bit microprocessors such as the 6800, 6801, 6803, 6808, 6809,
8051, 8085, Z80 and other popular types and their 16/32 bit counter parts in 8 bit data mode. The data bus inter­face consists of 8 data bits, write signal, chip select, and two address pins. All inputs are TTL-compatible (except
reset). The address pin control data transfer to the two internal D-type registers. Data is transferred according to
figure 7 and on the positive edge of the write signal.

Output

More
than 2
bits

Negative
difference

Input

Output

Less
than 2
bits

Positive
difference

Input

Output

Actual

Offset error

Endpoint
non-linearity

Full scale

Gain
error

Correct

Input

Figure 3. Errors in D/A conversion.
Differential non-linearity of more than
1 bit, output is non-monotonic.

Figure 4. Errors in D/A conversion.
Differential non-linearity of less than
1 bit, output is monotonic.

Figure 5. Errors in D/A conversion.
Non-linearity, gain and offset errors.

NJU39612

Current Direction, Sign1 & Sign

2

These bits are transferred from D7 when writing in the respective DA register. A0 must be set according to the data
transfer table in figure 7.

DA1 and DA

2

These are the two outputs of DAC1 and DAC2. Input to the DACs are internal data bus (Q61 … Q01) and (Q62 … Q02).

Reference Voltage V

V

is the analog input for the two DACs. Special care in layout, gives a very low voltage drop from pin to resistor.

Ref

Any V

between 0.0 V and VDD can be applied, but output might be non-linear above 3.0 V.

Ref

Ref

Power-on Reset

This function automatically resets all internal flip flops at power-on. This results in VSS voltage at both DAC outputs
and all digital outputs.

Reset

If Reset is not used, leave it disconnected. Reset can be used to measure leakage currents from VDD.

I [mA]

2

I

I [mA]

1

Figure 6a. Assuming that torque is
proportional to the current in resp.
winding it is possible to draw figure
8b.

CS A0 Data Transfer
0 0 D7 —> Sign1, (D6—D0) —> (Q61—Q01)
0 1 D7 —> Sign2, (D6—D0) —> (Q62—Q02)
1 X No Transfer

T [mNm]

2

T

max

T

nom

T

min

T [mNm]

1

Figure 6b. An example of acces­sible positions with a given torque
deviation/fullstep. Note that 1:st
µstep sets highest resolution. Data
points are exaggerated for illustra­tion purpose.
TNom = code 127.

Figure 7. Table showing how data is transfered inside NJU39612.

NJU39612

■ ABSOLUTE MAXIMUM RATINGS

Parameter Pin no. Symbol Min Max Unit

Voltage

Supply 4 V
Logic inputs 5-14,16 V
Reference input 1 V

DD
I
Ref

Current

Logic inputs 5-14,16 I

I

Temperature

Storage temperature T
Operating ambient temperature T

stg

opr

■ RECOMMENDED OPERATING CONDITIONS

Parameter Symbol Min Typ Max Unit

Supply voltage V
Reference voltage V

Rise and fall time of WR tr, t

DD
Ref

f

4.75 5.0 5.25 V
0 2.5 3.8 V

- - 1µs

- 6 V

-0.3 VDD+ 0.3 V

-0.3 VDD+ 0.3 V

-0.4 +0.4 mA

-55 +150 °C

-20 +85 °C

NJU39612

■ ELECTRICAL CHARACTERISTICS

Electrical characteristics over recommended operating conditions.

Parameter Symbol Conditions Min Typ Max Unit

Logic Input

Reset logic HIGH input voltage V
Reset logic LOW input voltage V
Logic HIGH input voltage V
Logic LOW input voltage V
Reset input current I
Input current, other inputs I

IHR
ILR

IH
IL

VSS < VIR < VDD -0.01 - 1 mA

IR

VSS < VI < V

I

DD

Input capacitance -3 -pF

Internal Timing Characteristics

Address setup time t
Data setup time t
Chip select setup time t
Address hold time t
Data hold time t
Chip select hold time t
Write cycle length t
Reset cycle length t

WR

res

Valid for A0 60 - - ns

as

Valid for D0 - D7 60 - - ns

ds
cs
ah
dh
ch

Reference Input

Input resistance R

ref

Logic Outputs

Logic HIGH output current I
Logic LOW output current I
Write propagation delay t

Reset propagation delay t

OH

OL

pwr

pres

DAC Outputs Reset open, V
Nominal output voltage V

VO = 2.4 V - -13 -5 mA
VO = 0.4 V 2 5 - mA
From positive edge of WR. - 30 100 ns
Outputs valid, C

= 120 pF

load

From positive edge of Reset to - 60 150 ns
outputs valid, C

DA

= 120 pF

load

= 2.5 V

Ref

Resolution - 7 - Bits
Offset error - 0.2 0.5 LSB
Gain error - 0.1 0.5 LSB
Endpoint nonlinearity - 0.2 0.5 LSB
Differential nonlinearity - 0.2 0.5 LSB
Load error (V

, unloaded - VDA, loaded) - 0.1 0.5 LSB

DA

R

= 2.5 kohm, Code 127 to DAC

load

Power supply sensitivity Code 127 to DAC - 0.1 0.3 LSB

Conversion speed t

4.75 V < V
For a full-scale transition to ±0.5 LSB - 3 8 µs

DAC

of final value, R

< 5.25 V

DD

load

= 2.5 kohm, C

= 50 pF.

load

3.5 - - V

- - 0.1 V

2.0 - - V

- - 0.8 V

-1 - 1 µA

70 - - ns

--0ns

--0ns

--0ns
50 - - ns
80 - - ns

6 9 - kohm

0-V

Ref

- 1LSB V

NJU39612

CS

A0

D0-D7

WR

DA

Sign

Figure 8. Timing

cs

t

as ah

t

ds

t

WR

tt

ch

t

t

dh

t

DAC

t

pwr

Reset

Sign

Figure 9. Timing of Reset

t

res

t

pres

NJU39612

■ APPLICATIONS INFORMATION

How Many Microsteps?

The number of true microsteps that can be obtained depends upon many different variables, such as the number of
data bits in the Digital-to-Analog converter, errors in the converter, acceptable torque ripple, single- or double-pulse
programming, the motor’s electrical, mechanical and magnetic characteristics, etc. Many limits can be found in the
motor’s ability to perform properly; overcome friction, repeatability, torque linearity, etc. It is important to realize that
the number of current levels, 128 (27), is
(reference voltage levels) available from each driver stage. Combining a current level in one winding with any of
128 other current levels in the other winding will make up 128 current levels. So expanding this, it is possible to get
16,384 (128 • 128) combinations of different current levels in the two windings. Remember that these 16,384 micro­positions are not all useful, the torque will vary from 100% to 0% and some of the options will make up the same
position. For instance, if the current level in one winding is OFF (0%) you can still vary the current in the other
winding in 128 levels. All of these combinations will give you the same position

Typical Application

The microstepper solution can be used in a system with or without a microprocessor.
Without a microprocessor, a counter addresses a ROM where appropriate step data is stored. Step and Direction
are the input signals which represent clock and up / down of counter. This is the ideal solution for a system where
there is no microprocessor or it is heavily loaded with other tasks.
With a microprocessor, data is stored in ROM / RAM area or each step is successively calculated. NJU39612 is
connected like any peripheral addressable device. All parts of stepping can be tailored for specific damping needs
etc. This is the ideal solution for a system where there is an available microprocessor with extra capacity and low
cost is more essential than simplicity. See typical application, figure 13.

not

the number of steps available. 128 is the number of current levels

but

a varying torque.

■ User Hints

Never disconnect ICs or PC Boards when power is supplied.
Select a motor that is rated for the current you need to establish desired torque. A high supply voltage will gain
better stepping performance even if the motor is not rated for the VMM voltage, the current regulation in the drivers
from New JRC will take care of it. A normal stepper motor might give satisfactory result, but while microstepping, a
“microstepping-adapted” motor is recommended. This type of motor has smoother motion due to two major differ­ences, the stator / rotor teeth relationship is non-equal and the static torque is lower.

The NJU39612 can handle programs which generate microsteps at a desired resolution as well as quarter

stepping, half stepping, full stepping, and wave drive.

Ramping

Every drive system has inertia which must be considered in the drive system. The rotor and load inertia play a big
role at higher speeds. Unlike the DC motor, the stepper motor is a synchronous motor and does not change its
speed due to load variations. Examining a typical stepper motor’s torque-versus-speed curve indicates a sharp
torque drop-off for the “start-stop without error” curve. The reason for this is that the torque requirements increase
by the cube of the speed change. For good motor performance, controlled acceleration and deceleration should be
considered even though microstepping will improve overall performance.

Time when motor is in
a compromise
position.

Time when micro
position is correct.

Write
signal.

Motor
position.

Writing to
channel 1.

Writing to
channel 2.

NJU39612

Double pulse write signal

Ideal data = desired position

Actual data = true position
Normal resolution

Write time = incorrect position

Figure 10. Double pulse programming, in- and output signals.

Time when motor is in
an intermediate
position.

Time when micro
position is almost
correct.

Write
signal.

Motor position. Note
that position is
a compromise.

Writing to
channel 1.

Writing to
channel 2.

always

Single pulse write signal

"Ideal data" = desired
position

Actual data = true position
Note increased resolution

Useful time = compromise position
with equally spaced angles

Useful time = correct

Time

position

Time

Useful time = almost
correct position

Figure 11. Single pulse programming, in- and output signals.

NJU39612

■ Programming NJU39612

There are basically two different ways of programming the NJU39612. They are called “single-pulse programming”
and “double-pulse programming.” Writing to the device can only be accomplished by addressing one register at a
time. When taking one step, at least two registers are normally updated. Accordingly there must be a certain time
delay between writing to the first and the second register. This programming necessity gives some special stepping
advantages.

Double-pulse Programming

The normal way is to send two write pulses to the device, with the correct addressing in between, keeping the delay
between the pulses as short as possible. Write signals will look as illustrated in figure10. The advantages are:

• low torque ripple

• correct step angles between each set of double pulses

• short compromise position between the two step pulses

• normal microstep resolution

Single-pulse Programming

A different approach is to send one pulse at a time with an equally-spaced duty cycle. This can easily be accom­plished and any two adjacent data will make up a microstep position. Write signals will look as in figure 11. The
advantages are:

• higher microstep resolution

• smoother motion
The disadvantages are:

• higher torque ripple

• compromise positions with almost-correct step angles

NJU39612

Counter

PROM

CE

Clock Up/Dn

Step

D0-D7

Direction

Control Logic

Figure 12. Typical blockdiagram of an application without a microprocessor.

V (+5 V)

CC

0.1 F 0.1 F

NJU39612

A0

WR
CS

Vref

Voltage

Reference

NJM3777

+

10 F

V

MM

4

To

P

+2.5V

13

D0

6

D7

14

16
20

GND
(V )

CC MM

NJU39612

A0

5

WR
CS

RESET

1

VV

Ref

V

DD

SS

17

Sign

DA

Sign

DA

3

1

2

1

18

2

19

2

+5 V

10
11

8

15
14
17

12

12 k

4700 pF

Figure 13. Typical application in a microprocessor based system.

Phase
Dis

1

V

R1

Phase
Dis

2

V

R2

RC

13 5 20

V

CC

1

VV

NJM3777

2

11

6, 7,
18, 19

9

0.47 0.47

MM1 MM2

2

3

16

R

S

M

M

M

M

22

4

A1

2

B1

21

A2

23

B2

ECECGND

2

STEPPER

MOTOR

Pin numbers refer
to EMP package.

R

S

GND (V

)

The specifications on this databook are only

given for information , without any guarantee
as regards either mistakes or omissions.
The application circuits in this databook are
described only to show representative
usages of the product and not intended for
the guarantee or permission of any right
including the industrial rights.