L6226Q Ver la hoja de datos (PDF) - STMicroelectronics
Número de pieza
componentes Descripción
Fabricante
L6226Q Datasheet PDF : 29 Pages
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Circuit description
4.3
Truth table
Table 7.
Truth table
Inputs
EN
IN1
L
X (1)
H
L
H
H
H
L
H
H
1. X = Don't care
2. High Z = High impedance output
L6226Q
Outputs
IN2
OUT1
OUT2
X
High Z (2)
High Z
L
GND
GND
L
Vs
GND
H
GND
Vs
H
Vs
Vs
4.4
Non-dissipative overcurrent detection and protection
An overcurrent detection circuit (OCD) is integrated. This circuit can be used to provides
protection against a short circuit to ground or between two phases of the bridge as well as a
roughly regulation of the load current. With this internal over current detection, the external
current sense resistor normally used and its associated power dissipation are eliminated.
Figure 9 shows a simplified schematic of the overcurrent detection circuit for the bridge A.
bridge B is provided of an analogous circuit.
To implement the over current detection, a sensing element that delivers a small but precise
fraction of the output current is implemented with each high side power MOS. Since this
current is a small fraction of the output current there is very little additional power
dissipation. This current is compared with an internal reference current IREF. When the
output current reaches the detection threshold Isover the OCD comparator signals a fault
condition. When a fault condition is detected, an internal open drain MOS with a pull down
capability of 4 mA connected to OCD pin is turned on. Figure 10 shows the OCD operation.
This signal can be used to regulate the output current simply by connecting the OCD pin to
EN pin and adding an external R-C as shown in Figure 9. The off time before recovering
normal operation can be easily programmed by means of the accurate thresholds of the
logic inputs.
IREF and, therefore, the output current detection threshold are selectable by RCL value,
following the equations:
● Isover = 2.8 A ± 30 % at -25 °C < TJ < 125 °C if RCL = 0 Ω
(PROGCL connected to GND)
●
Isover =
1----1---0----5---0--
RCL
±10 % at -25 °C < TJ < 125 °C if 5 kΩ < RCL < 40 kΩ
Figure 11 shows the output current protection threshold versus RCL value in the range 5 kΩ
to 40 kΩ.
The disable time tDISABLE before recovering normal operation can be easily programmed by
means of the accurate thresholds of the logic inputs. It is affected whether by CEN and REN
12/29
Doc ID 14335 Rev 5
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