5829 Datasheet, PDF (9/12 Pages) Allegro MicroSystems – 9-BIT SERIAL-INPUT, LATCHED SINK DRIVER

5829
9-BIT SERIAL-INPUT,
LATCHED SINK DRIVER
The chopping function is disabled when V_REF > 4.5 V. To prevent
operation at higher than allowable current levels, V_REF should not
exceed 3.2 V, except to disable the chopping function.
DUTY CYCLE LIMITS
For correct operation of the UCN5829EB, the duty cycle must
be between 15% and 50% with 20% to 40% recommended. The lower
limit is due to internal lockout circuitry while the upper limit guarantees
synchronous operation. The duty cycle (dc) can be calculated as
dc =
t_on
I_OUT(P) / I_OUT(asym) + v_d / v_c
≈
t_on + t_off
1 + v_d / v_c
where I_OUT(asym) = the asymptotic current value = v_c/R_L
v_d = discharge voltage across the load = V_HSD + V_DIODE
v_c = charge voltage across the load = V_BB - V_OUT(SAT) - V_HSD
For most practical cases, correct operation can be achieved if
I_OUT(asym) / I_OUT(P) > 2.5.
GENERAL
For applications with 9-wire printheads, SERIAL DATA OUT
should be connected to IN₉. For 24-wire printhead applications, three
devices (eight channels per device) are cascaded by connecting
SERIAL DATA OUT to the next SERIAL DATA IN.
Each of the CMOS logic inputs have internal pull-up resistors for
TTL compatibility.
An external transient-protection flyback diode is required at each
output. Fast recovery diodes are recommended to reduce power
dissipation in the UCN5829EB. Internal filtering prevents false trigger-
ing of the current sense comparator which can be caused by the
recovery current spike of the diodes when the outputs turn ON.
The SUPPLY terminal should be well decoupled with a capacitor
placed as close as possible to the device. Internal power-ON reset
circuitry prevents false output triggering during power up.
Thermal protection circuitry is activated and turns OFF all drivers
at a junction temperature of typically +165°C. The thermal shutdown is
independent of all other functions. It should not be used as another
control input but is intended only to protect the chip from catastrophic
failures due to excessive junction temperatures. The output drivers are
re-enabled when the junction temperature cools down to approximately
+145°C.