L6258

Manufacturer Part NumberL6258
ManufacturerSTMicroelectronics
L6258 datasheet
 


Specifications of L6258

Operating Current15mAMotor Controller TypePWM Motor Controller
Package TypePowerSOOperating Supply Voltage (min)12V
Operating Supply Voltage (typ)34VOperating Supply Voltage (max)5.25V
Lead Free Status / Rohs StatusNot Compliant  
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PWM current control loop
3
PWM current control loop
3.1
Open loop transfer function analysis
Block diagram: refer to
Input parameters:
V
= 24V
S
L
= 12mH
L
R
= 12Ω
L
R
= 0.33Ω
S
R
= to be calculated
C
C
= to be calculated
C
Gs transconductance gain = 1/Rb
Gin transconductance gain = 1/Ra
Ampl. of the Tria_0_180 ref. = 1.6V (peak to peak)
R
= 40KΩ
a
R
= 20KΩ
b
V
= Internal reference equal to V
r
these data refer to a typical application, and will be used as an example during the analysis
of the stability of the current control loop.
The block diagram shows the schematics of the L6258 internal current control loop working
in PWM mode; the current into the load is a function of the input control voltage V
the relation between the two variables is given by the following formula:
where:
V
is the control voltage defining the load current value
DAC
G
is the gain of the input transconductance amplifier ( 1/Ra )
in
G
is the gain of the sense transconductance amplifier ( 1/Rb )
s
R
is the resistor connected in series to the output to sense the load current
s
In this configuration the input voltage is compared with the feedback voltage coming from
the sense resistor, then the difference between this two signals is amplified by the error
amplifier in order to have an error signal controlling the duty cycle of the output stage
keeping the load current under control.
It is clear that to have a good performance of the current control loop, the error amplifier
must have an high DC gain and a large bandwidth.
16/32
Figure 5.
/2 (Typ. 2.5V)
DD
I
· R
· G
= V
LOAD
S
S
DAC
1
-------
I
R S
=
V
LOAD
DAC
R
b
R b
-------------------
I
=
V
=
LOAD
DAC
R
R
a
s
DAC
· G
in
1
-------
R a
V
DAC
( )
-------------- - A
0.5
R
S
L6258
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