l9958 STMicroelectronics, l9958 Datasheet - Page 23

• Manufacturer Part Number: l9958
• Description: Low Rdson Spi Controlled H-bridge
• Manufacturer: STMicroelectronics

L9958
5.3
5.3.1
5.3.2
Off-state diagnosis
This diagnostic is performed in any off-state condition, just after ignition key-on or during an
off-state phase occurring after an on-state phase of the bridge.
Off-state detection scheme
In order to avoid any wrong diagnostic, a filtering time "Tdiag_off" is applied before
performing the detection if the bridge was in on-state before. This filtering time is not applied
in case of detection after key on.
Figure 18. Off-state detection scheme
Open load detection
An equivalent resistor of 100 kΩ (typ.) is targeted for open-load detection.
In order to avoid any unwanted supply of the bridge through the high-side transistor body
diode during off-state measurement, the current source is connected only if Vs is higher
than the Vs under-voltage threshold.
Figure 19. Open load detection
The diagnostic is based on a closed loop voltage control on OUT1 and associated current
measurement.
A voltage amplifier forces a constant voltage on OUT1 through two current sources (high-
side source and low-side current sink). The OUT2 is pulled-down through a constant current
sink. Based on the current flowing out of the amplifier (Ip – In) compared to several current
thresholds, open-load as well as short-circuit to ground and battery can be detected.
POR
DI
EN
DIAG
SPI
Diag
Done
OFF
Diag
Done
No
Diag
ON
No
Diag
Doc ID 17269 Rev 1
No
Diag
T
No
Diag
diag_off
10 k
No
Diag
OFF
Typical value
for detection
No
Diag
100 k
Diag
Done
200 k
Diag
Done
No
Diag
ON
No
Diag
AC00669
No
Diag
Diagnostics and protections
No
Diag
OFF
T
diag_off
No
Diag
No
Diag
ON
No
Diag
OFF
No
Diag
SLEEP
AC00668
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