L4979DTR-E STMicroelectronics, L4979DTR-E Datasheet - Page 11

• Manufacturer Part Number: L4979DTR-E
• Description: IC REG PROGR WATCHDOG 8SOIC
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r
• Series: -r

Specifications of L4979DTR-E

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 5V
• Current - Output: 150mA
• Voltage - Input: 5.6 ~ 31 V
• Operating Temperature: -40°C ~ 150°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.236", 6.0mm Width)
• Power - Output: *
• Regulator Topology: Positive Fixed
• Voltage - Dropout (typical): 0.2V @ 150mA
• Number Of Regulators: 1
• Current - Limit (min): 150mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

3.3
Table 10.
Watchdog
The watchdog input W
reset output R
thorough the external capacitor C
the constant current I
generated. To prevent this reset, the microcontroller must generate a positive edge during
the discharge of the capacitor before the voltage has reached the threshold V
calculate the minimum time T
edge, the following equation can be used:
Each W
happens when the lower V
threshold V
voltage at the watchdog timer capacitor C
Figure 4.
i
positive edge switches the current source from discharging to charging; the same
whth
Reset time diagram
Watchdog time diagram
es
the current switches from charging to discharging. The result is a saw tooth
is set to low. The pulse sequence time can be set within a wide range
cwd
i
monitors a connected microcontroller. If pulses are missing, the
. If the lower threshold V
wlth
(
V
dis
whth
Doc ID 10262 Rev 7
threshold is reached. When the voltage reaches the upper
during which the microcontroller must generate the positive
tw
. The watchdog circuit discharges the capacitor C
–
V
wlth
tw
)
.
×
C
tw
wlth
=
is reached, a watchdog reset is
I
cwd
×
T
dis
wlth
. In order to
tw
11/22
with