NJM3777E3 NJR, NJM3777E3 Datasheet - Page 7

• Manufacturer Part Number: NJM3777E3
• Description: IC STEPPER MOTOR DVR DUAL 24-EMP
• Manufacturer: NJR
• Type: Stepper Motor Controller/Driverr

Specifications of NJM3777E3

• Applications: Stepper Motor Driver, 2 Phase
• Number Of Outputs: 1
• Current - Output: 800mA
• Voltage - Load: 10 V ~ 40 V
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -20°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 24-EMP
• Product: Stepper Motor Controllers / Drivers
• Operating Supply Voltage: 7 V
• Supply Current: 85 mA
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Current sense filtering
winding. To prevent this spike from reseting the flip-flops through the current sensing comparators, the clock
oscillator generates a blanking pulse at turn-on. The blanking pulse pulse disables the comparators for a short time.
Thereby any voltage transient across the sensing resistor will be ignored during the blanking time.
value. The time is calculated as:
t
As the C
possible. Nominal value is 4 700 pF, which gives a blanking time of 1.0 s.
motor current, will reach a slightly higher level than what is defined by the reference voltage. The filtering delay also
limits the minimum possible output current. As the output will be on for a short time each cycle, equal to the digital
filtering blanking time plus additional internal delays, an amount of current will flow through the winding. Typically
this current is 1-10 % of the maximum output current set by R
with the comparator C input. In this case the digital blanking time should be as short as possible. The recom-
mended filter component values are 1 kohm and 820 pF. Lowering the switching fre- quency also helps reducing
the minimum output current.
Switching frequency
The frequency of the clock oscillator is set by the timing components R
filter blanking time, the clock oscillator frequency is adjusted by R
frequency is approximately calculated as:
f
Nominal component values of 12 kohm and 4 700 pF results in a clock frequency of 23.0 kHz. A lower frequency
will result in higher current ripple, but may improve low level linearity. A higher clock frequency reduces current
ripple, but increases the switching losses in the IC and possibly the iron losses in the motor.
Phase inputs
A logic HIGH on a Phase input gives a current flowing from pin M
A logic LOW gives a current flow in the opposite direction. A time delay prevents cross conduction in the H-bridge
when changing the Phase input.
Figure 8. Typical thermal resistance vs. PC Board
copper area and suggested layout
At turn-on a current spike occurs, due to the recovery of the recirculation diodes and the capacitance of the motor
b
s
80
70
60
50
40
30
20
= 1 / ( 0.77 • R
Choose the blanking pulse time to be longer than the duration of the switching transients by selecting a proper C
= 210 • C
As the filtering action introduces a small delay, the peak value across the sensing resistor, and hence the peak
When optimizing low current performance, the filtering may be done by adding an external low pass filter in series
To create an absolute zero current, the Dis input should be HIGH.
Thermal resistance [ C/W]
EMP package
5
PCB copper foil area [cm ]
T
10
value may vary from approximately 2 200 pF to 33 000 pF, a blanking time ranging from 0.5 s to 7 s is
T
[s]
15
T
20
• C
T
25
)
2
30
35
24-pin
EMP
Figure 9. Stepping modes
Phase
Phase
Dis
Dis
–100%
–140%
–100%
–140%
V
140%
100%
V
140%
100%
I
140%
100%
I
140%
100%
MA1
MA2
R1
R2
1
2
2
1
S
.
Full step mode
A
T
. The value of R
into pin M
T
and C
B
.
T
at the RC-pin. As C
Half step mode
T
is limited to 2 - 20 kohm. The
NJM3777
Modified half step mode
T
sets the digital
T