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.