JRC NJU3962E2 Datasheet

NJU39612

Figure 1. Block Diagram

Ref

D7 - D0

RESET

Sign

D / A

POR

NJU39612

DA- Data 1

DA- Data 2

■ FEATURES

• Analog control voltages from 3V down to 0.0V

• High-speed microprocessor interface

• Full -scale error ±1 LSB

• Fast conversion speed 3 µs

• Matches the dual stepper motor drivers

• Package EMP20

■ BLOCK DIAGRAM

NJU39612E2

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).

MICROSTEPPING MOTOR CONTROLLER WITH DUAL DAC

■ GENERAL DESCRIPTION ■ PACKAGE OUTLINE

NJU39612

Figure 2. Pin configuration

1 2 3 4 5 6 7 8 9

18 17

16 15

14 13 12 11

ref

Sign

VDD

Reset

Sign

D3 D2

NJU39612E2

■ PIN CONFIGURATION

■ PIN DESCRIPTION

Refer to figure 2.

EMP Symbol Description

Ref

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

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

ref

- 1 LSB.

3 Sign

Sign 1, TTL/CMOS level. To be connected directly to NJM377x phase input. Databit D7 is transfered non inverted from NJU39612 data input.

Voltage Drain-Drain, logic supply voltage. Normally +5 V.

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

edge. 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

channel 2 (A0 = HIGH). 15 NC Not connected 16 CS Chip Select, TTL/CMOS level, input to select chip and activate data transfer from data inputs. LOW level

= chip is selected. 17 V

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

noted. 18 Sign

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

non-inverted from NJU39612 data input. 19 DA

Digital-to-Analog 2, voltage output. Output between 0.0 V and V

ref

- 1 LSB.

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

Res

≥ 3.5 V = HIGH level. Pulled low

internally.

NJU39612

Endpoint non-linearity

Offset error

Actual

Gain error

Output

Input

Full scale

Correct

Less than 2 bits

Positive difference

Output

Input

More than 2 bits

Negative difference

Output

Input

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

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

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

■ 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.

NJU39612

T [mNm]

max

nom

min

I [mA]

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

Current Direction, Sign1 & Sign

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

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

Ref

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

Any V

Ref

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

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.

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

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

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