NJM#37770D3 NJR, NJM#37770D3 Datasheet - Page 4

• Manufacturer Part Number: NJM#37770D3
• Description: Motor / Motion / Ignition Controllers & Drivers 60V Hi-Perf Stpr
• Manufacturer: NJR
• Type: Stepper Motor Driverr

Specifications of NJM#37770D3

• Product: Stepper Motor Controllers / Drivers
• Operating Supply Voltage: 5 V
• Supply Current: 65 mA
• Mounting Style: Through Hole
• Package / Case: DIP-16
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Current level selection.
selected according to the table below.
the sensing resistor R
Current sensor
current levels. The motor current is sensed as a voltage drop across the current sensing resistor, R
one of the voltage references from the divider. When the two voltages are equal, the comparator triggers the single-pulse
generator. Only one comparator at a time is activated by the input logic.
Single-pulse generator
multivibrator output is high during the pulse time, t
Output stage
diodes are connected to the circuit externally. The two sinking transistors are used to switch the power supplied to the
motor winding, thus driving a constant current through the winding. See figures 3 and 4.
Overload protection
will be reduced if the maximum permissible junction temperature is exceeded. It should be noted, however, that it is not
short circuit protected.
Operation
low-pass filter, R
above the comparator threshold voltage, the monostable is triggered and its output turns off the conducting sink
transistor.The polarity across the motor winding reverses and the current is forced to circulate through the appropriate
upper protection diode back through the source transistor (see figure 3, arrow 2).
below the comparator threshold level.The sinking transistor then turns on and the motor current starts to increase again,
The cycle is repeated until the current is turned off via the logic inputs.When both I
the output H-bridge are turned off, which means that inductive current recirculates through two opposite free-wheeling
diodes (see figure 3, arrow 3). this method of turning off the current results in a faster current decay than if only one
transistor was turned off and will therefore improve speed performance in half-stepping mode.
- 4 -
The status of I
Motor current
High level
Medium level
Low level
Zero current
The specific values of the different current levels are determined by the reference voltage V
The peak motor current can be calculated as follows:
i
The motor current can also be continuously varied by modulating the voltage reference input.
The current sensor contains a reference voltage divider and three comparators for measuring each of the selectable
The pulse generator is a monostable multivibrator triggered on the positive edge of the comparator output. The
t
The single pulse switches off the power feed to the motor winding, causing the winding to decrease during t
If a new trigger signal should occur during t
The output stage contains four transistors and two diodes, connected in an H-bridge. Note that the upper recirculation
The circuit is equipped with a thermal shut-down function, which will limit the junction temperature. The output current
When a voltage V
i
R = Winding resistance
L = Winding inductance
t = time
(see figure 3, arrow 1)
The motor current appears across the external sensing resistor, R
After the monostable has timed out, the current has decayed and the analog voltage across the sensing resistor is
m
m
off
= (V
= (V
= 0.69 • R
R
MM
• 0.080) / R
/ R) • (1 - e
T
• C
C
0
C
and I
T
C
MM
, to the voltage comparator input (DIP pin 10, EMP pin 12). At the moment the sensed voltage rises
100%
S
S
-(R • t ) / L
60%
20%
.
[A], at 100% level
is applied across the motor winding, the current rise follows the equation:
0%
1
inputs determines the current level in the motor winding. Three fixed current levels can be
)
I
L
H
L
H
0
I
L
L
H
H
1
off
, it is ignored.
off
, which is determined by the timing components R
S
, as an analog voltage. This voltage is fed through a
1
and I
0
are high, all four transistors in
R
together with the value of
S
, and compared with
T
and C
Ver.2006-04-11
off
T
.
.