L6258E STMicroelectronics, L6258E Datasheet - Page 16

• Manufacturer Part Number: L6258E
• Description: IC MOTOR DRIVER UNIV 36-PWRSOIC
• Manufacturer: STMicroelectronics
• Type: DMOS Dual Full Bridge Driverr

Specifications of L6258E

• Applications: DC Motor Driver, Stepper Motor Driver
• Number Of Outputs: 2/1
• Current - Output: 1.2A
• Voltage - Load: 12 V ~ 40 V
• Voltage - Supply: 4.75 V ~ 5.25 V
• Mounting Type: Surface Mount
• Package / Case: PowerSO-36 Exposed Bottom Pad
• Operating Supply Voltage: 12 V to 40 V
• Mounting Style: SMD/SMT
• Operating Temperature: 150 C
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Operating Temperature: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-1433-5

PWM current control loop
3
3.1
16/31
PWM current control loop
Open loop transfer function analysis
Block diagram: refer to
Input parameters:
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●
●
●
●
●
●
●
●
●
●
●
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 L6258E internal current control loop
working in PWM mode; the current into the load is a function of the input control voltage
V
where:
V
G
G
R
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.
DAC
DAC
s
in
s
V
L
R
R
R
C
Gs transconductance gain = 1/Rb
Gin transconductance gain = 1/Ra
Ampl. of the Tria_0_180 ref. = 1.6V (peak to peak)
R
R
V
, and the relation between the two variables is given by the following formula:
L
S
r
L
S
C
C
a
b
= Internal reference equal to V
= 12mH
= 12Ω
= 40KΩ
= 20KΩ
= 24V
= 0.33Ω
= to be calculated
= to be calculated
is the resistor connected in series to the output to sense the load current
is the control voltage defining the load current value
is the gain of the input transconductance amplifier ( 1/Ra )
is the gain of the sense transconductance amplifier ( 1/Rb )
Figure 5.
I
LOAD
I
LOAD
Doc ID 8688 Rev 9
I
=
LOAD
V
⋅
DAC
R S
· R
DD
/2 (Typ. 2.5V)
⋅
S
⋅
· G
-------
R b
--------------------- -
R a
1
S
R
⋅
=
= V
b
R s
V
DAC
DAC
=
· G
0.5
⋅
-------
R a
in
1
⋅
V
-------------- - A
R S
DAC
( )
L6258E