L6258E STMicroelectronics, L6258E Datasheet - Page 19

• 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

L6258E
3.4
Before analysing the error amplifier block and the sense transconductance block, we have to
do this consideration:
Aloop
Ax|
and
Bx|
this means that Ax|dB is the sum of the power amplifier and load blocks;
Ax|
The BODE analysis of the transfer function of Ax is:
Figure 7.
The Bode plot of the Ax|dB function shows a DC gain of -1.9dB and a pole at 163Hz.
It is clear now that (because of the negative gain of the Ax function), Bx function must have
an high DC gain in order to increment the total open loop gain increasing the bandwidth too.
Error amplifier and sense amplifier
As explained before the gain of these two blocks is:
Bx
Being the voltage across the sense resistor the input of the Bx block and the error amplifier
voltage the output of the same, the voltage gain is given by:
dB
dB
dB
dB
= ACerr
dB
= ACpw|
= ACerr|
= (29,5) + (-31.4) = -1.9dB
= Ax
Ax bode plot
dB
dB
dB
dB
+ Bx
+ ACsense
+ ACsense|
+ ACload|
dB
ib
dB
dB
dB
=
Doc ID 8688 Rev 9
Vsense
⋅
Gs
=
Vsense
⋅
------- -
Rb
1
PWM current control loop
19/31