L295 Просмотр технического описания (PDF) - STMicroelectronics
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L295 Datasheet PDF : 8 Pages
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L295
APPLICATION CIRCUIT
D2, D4 = 2A High speed diodes
D1, D3 = 1A High speed diodes
R1 = R2 = 2Ω
L1 = L2 = 5 mH
) trr ≤ 200 ns
FUNCTIONAL DESCRIPTION
The L295 incorporates two indipendent driver
channals with separate inputs and outputs, each
capable of driving an inductive load (see block
diagram).
The device is controlled by three micriprocessor
compatible digital inputs and two analog inputs.
These inputs are:
EN
chip enable (digital input, active low),
enables both channels when in the low
state.
Vin1, Vin2
channel inputs (digital inputs, active
high), enable each channel inde-
pendently. A channel is actived when
both EN and the appropriate channel
input are active.
Vref1, Vref2 referce voltages (analog inputs), used
to program the peak load currents.
Peak load current is proportional to Vref
.
Since the two channels are identical, only channel
one will be described.
The following description applies also the channel
two, replacing FF2 for FF1, Vref for Vref1 etc.
When the channel is avtivated by low level on the
EN input and a high level on the channel input, Vin2,
the output transistors Q1 and Q2 switch on and
current flows in the load according to the exponen-
tial law:
I=
V
R1
(1 − e
− R1 t
L1
)
where:
R1 and R2 are the resistance and in-
ductance of the load and V is the volt-
age available on the load (Vs - Vdrop -
Vsense).
The current increases until the voltage on the ex-
ternal sensing resistor, RS1, reaches the reference
voltage, Vref1. This peak current, Ip1, is given by:
Ip1 =
Vref1
RS1
At this point the comparator output, Vomp1, sete
the RS flip-flop, FF1, that turns off the output tran-
sistor, Q1. The load current flowing through D2, Q2,
RS1, decreases according to the law:
I=(
VA
R1
+ Ip1 )
e
− R1 t
L1
−
VA
R1
where VA = VCEsat Q2 + Vsense + VD2
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