5829 Datasheet, PDF (10/12 Pages) Allegro MicroSystems – 9-BIT SERIAL-INPUT, LATCHED SINK DRIVER

5829
9-BIT SERIAL-INPUT,
LATCHED SINK DRIVER
TYPICAL APPLICATION
Shown is a typical application with the UCN5829EB controlling
a chop current of 1 A through a 3 mH, 9 Ω load. To check the duty
cycle and I_OUT(asym)/I_OUT(P) restrictions
where v_d = V_HSD + V_DIODE ≈ 1.5 + 1.5 = 3
v_c = V_BB - V_OUT(SAT) - V_HSD = 36 - 1.5 - 1.5 = 33
I_OUT(asym) = v_c / R_L = 33 / 9 = 3.67
then
I_OUT(asym) / I_OUT(P) = 3.67 / 1 = 3.67
The condition of I_OUT(asym) / I_OUT(P) > 2.5 is met and the duty cycle will
be within the proscribed limits. The actual duty cycle is
dc = ^{IOUT(P) /IOUT(asym) + vd/vc} = ^{1.0/3.67 + 2.5/33}
1 + v_d/v_c
1 + 2.5/33
= 32%
For a 50 kHz chopping frequency and a 250 µs print enable time, the
remaining component values are
with
then
and
C_C = 250 pF and C_EN = 0.01 µF
R_C = 1/(2 f_ch C_C) = 1/(2 x 50 x 10³ x 250 x 10^-12) = 40 kΩ
R_EN = t_EN / C_EN = 250 x 10^-6 / 10 x 10^-9 = 25 kΩ
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