A29040AL-90 AMIC Technology, A29040AL-90 Datasheet - Page 4

• Manufacturer Part Number: A29040AL-90
• Description: 512K X 8 Bit CMOS 5.0 Volt-only/ Uniform Sector Flash Memory
• Manufacturer: AMIC Technology

PWM CURRENT CONTROL
designed to drive both windings of a bipolar
stepper motor. Output current is sensed and
controlled independently in each bridge by
an external sense resistor (R
comparator, and monostable multivibrator.
increases in the motor winding and flows
through the external sense resistor until the
sense voltage (V
the comparator’s input:
monostable, which turns OFF the source
driver of the bridge. The actual load current
peak will be slightly higher than the trip point
(especially for low-inductance loads) be-
cause of the internal logic and switching
delays. This delay (t
turn-off, the motor current decays, circulating
through the ground-clamp diode and sink
transistor. The source driver’s OFF time
(and therefore the magnitude of the current
decrease) is determined by the monostable’s
external RC timing components, where
t
100 k and 100 pF to 1000 pF.
the winding current (the sense voltage) is
again allowed to rise to the comparator’s
threshold. This cycle repeats itself, maintain-
ing the average motor winding current at the
desired level.
may cause current spikes capable of tripping
the comparator, resulting in erroneous
current control. An external R
should be used to delay the action of the
comparator. Depending on load type, many
applications will not require these external
components (SENSE connected to E).
off
2919
DUAL FULL-BRIDGE
MOTOR DRIVER
= R
The A2919SB/SLB dual bridges are
When the bridge is turned ON, current
The comparator then triggers the
When the source driver is re-enabled,
Loads with high distributed capacitances
T
C
T
within the range of 20 k
I
TRIP
S
) reaches the level set at
= V
d
) is typically 2 s. After
REF
/10 R
S
), internal
C
S
C
C
time delay
to
APPLICATIONS INFORMATION
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
V
I
OUT
PHASE
0
+
–
PWM OUTPUT CURRENT WAVE FORM
LOAD CURRENT PATHS
R S
t
d
V
BB
BRIDGE ON
SOURCE OFF
ALL OFF
t
I
off
TRIP
Dwg. EP-006-1
Dwg. WM-003-1A