Preliminary
TS4268
180mA Ultra Low Dropout Voltage Regulator
with Reset & Watchdog Function
SOP-8
Pin Definition:
1.
Input
2. N/C
3. Reset Output
4. Ground
8. Output
7. Watchdog
6. Radj
5. Reset Delay
General Description
TS4268 is a low dropout voltage regulator. The maximum input voltage is 45 V. It can deliver an output current of at
least 180mA. TS4268 is short circuit proof and features temperature protection that disables the circuit in the event of
impermissibly high temperatures. The watchdog function is disabled as a function of the load, so that a controller is not
interrupted during sleep mode by a watchdog reset.
Application Description
TS4268 regulates an input voltage in the range 5.5V ~ 45V. In the event of an output voltage Vout < V
RT
,
a
reset signal
is generated. The wiring of the reset switching threshold input enables the value of V
RT
to be reduced. The reset delay
time can be adjusted using an external capacitor. The integrated watchdog monitors the connected active controller. If
there is no positive going edge at the watchdog input, the reset output is set to low. The reset delay capacitor provides
a wide adjustment range for the pulse repetition time. The watchdog function is only activated if the load exceeds 8mA.
This ensures that a microcontroller is not activated during power-down and the current drain is not increased.
Features
●
●
●
●
●
●
●
●
●
●
Output voltage tolerance < ± 2 %
Very low current consumption
Low-drop voltage
Watchdog
Settable reset threshold
Over temperature protection
Reverse polarity protection
Short-circuit proof
Suitable for use in automotive electronics
Wide temperature range
Ordering Information
Part No.
TS4268CS50 RL
Package
SOP-8
Packing
2.5Kpcs/ 13” Reel
Pin Description
Pin No.
1
2
3
4
5
6
7
8
Symbol
IN
N/C
RO
GND
RD
RADJ
WI
OUT
Pin Description
Input Voltage.
block to ground directly with ceramic capacitor
Not Connected
Reset Output.
the open collector output is connected to the 5V output via an
integrated resistor of 30kΩ
Ground
Reset Delay.
connect a capacitor to ground for delay time adjustment.
Reset Switching Threshold.
for setting the switching threshold, output to ground with
voltage divider. If this input is connected to ground, the reset is triggered at an output
voltage of 4.5V.
Watchdog Input.
positive-edge-triggered input for monitoring a microcontroller.
Output Voltage.
block to ground with 22uF capacitor, ESR <3Ω
1/7
Version: Preliminary
Preliminary
TS4268
180mA Ultra Low Dropout Voltage Regulator
with Reset & Watchdog Function
Circuit Description
The control amplifier compares a reference voltage, which is kept highly accurate by resistance adjustment, to a
voltage that is proportional to the output voltage and drives the base of the series transistor via a buffer. Saturation
control as a function of the load current prevents any over-saturation of the power element. If the externally scaled
down output voltage at the reset threshold input drops below 1.35V, the external reset delay capacitor is discharged by
the reset generator. If the voltage on the capacitor reaches the lower threshold V
ST
, a reset signal is generated on the
reset output and not cancelled again until the upper threshold voltage is exceeded. If the reset threshold input is
connected to GND, reset is triggered at an output voltage of 4.5V. A connected microcontroller is monitored by the
watchdog logic. If pulses are missing, the rest output is set to low. The pulse sequence time can be set within a wide
range with the reset delay capacitor. TS4268 is also incorporates a member of internal circuits for protection against:
•
Over load
• Over temperature
• Reverse polarity
Block Diagram
2/7
Version: Preliminary
Preliminary
TS4268
180mA Ultra Low Dropout Voltage Regulator
with Reset & Watchdog Function
Absolute Maximum Ratings
Parameter
Input
Input voltage
Input current
Reset Output
Voltage
Current
Reset Delay
Voltage
Current
Watchdog
Watchdog input
Reset Input
Reset threshold
Output
Output voltage
Output current
Ground
Current
Temperatures
Junction temperature
Storage temperature
Tj
Tstg
-40
-50
150
150
°C
Iq
-100
50
mA
Vout
Iout
-0.3
7
Internally limited
V
V
RT
-0.3
7
V
Vwi
-0.3
7
V
V
RD
I
RD
-0.3
7
Internally limited
V
Vres
Ires
-0.3
7
Internally limited
V
Vin
Iin
-30
45
Internally limited
V
Symbol
min.
max.
Unit
Notes
Operation Range
Parameter
Input voltage
Junction temperature
Symbol
Vin
Tj
min.
--
-40
max.
45
150
Unit
°C
Notes
Thermal Resistance
Parameter
Junction to ambient (soldered)
Junction pin
Symbol
Rθja
Rθjp
min.
--
--
max.
185
72
Unit
°C/W
(note 1)
(note 2)
Notes
1. Package mounted on PCB 80 x 80 x 1.5mm3, footprint only, zero airflow.
2. Measure to pin 2
Operation at up to the maximum junction temperature of 150°C is possible in principle. Note, however, operation at the
maximum permitted rating could be affected the reliability of the device.
3/7
Version: Preliminary
Preliminary
TS4268
180mA Ultra Low Dropout Voltage Regulator
with Reset & Watchdog Function
Electrical Characteristics
(Vin=13.5V, -40
≤
Tj
≤1
25 C, unless otherwise specified.)
o
Parameter
Output Voltage
Current Limit
Quiescent Current
Dropout Voltage (note 1)
Line Regulation
Load Regulation
Reset Function
Reset threshold
Reset adjust threshold
Reset low voltage
Saturation voltage
Charging current
Upper reset timing threshold
Reset delay time
Reset reaction time
Pull-up
Lower reset timing threshold
Watchdog Input
Discharge current
Charging current
Upper timing threshold
Lower timing threshold
Watchdog periode
Watchdog trigger time
Activating current
Slew rate
V
RD
< 1.0V
V
RD
< 1.0V
Vout= 0
Iq= 0mA
Iq= 100mA
I
L
=150mA
Test Conditions
5mA
≤
I
L
≤
150mA, 6V
≤
Vin
≤
28V
Min
4.90
180
--
--
--
--
--
4.20
1.28
Typ
5.00
250
300
13
250
10
10
4.50
1.35
0.20
0.03
12
1.8
15
2
30
0.40
3.5
12
1.8
0.40
55
40
8
--
Max
5.10
--
400
20
500
30
30
4.80
1.45
0.50
0.10
18
2.2
25
--
46
0.55
5.2
18
2.2
0.55
75
60
15
--
Unit
V
mA
uA
mA
mV
mV
mV
V
V
V
V
uA
V
mS
uS
KΩ
V
uA
uA
V
V
mS
mS
mA
V/us
6V≤ Vin
≤28V,
I
L
=150mA
5mA≤ I
L
≤150mA
1mA external
Vout < V
RT
V
RD
< 1.0V
C
RD
= 100nF
C
RD
= 100nF
With resp. to Vout
--
--
5
1.4
10
--
18
0.20
1.5
5
1.4
0.20
C
RD
= 100nF
C
RD
= 100nF
Activates watchdog
from 20% up to 80% Vout
30
25
2
5
Note 1: Drop voltage = Vin - Vout (measured when the output voltage has dropped 100 mV from the nominal value
obtained at 13.5 V input)
Note 2: The reset output is low in range from Vout = 1V to Vout,rt.
4/7
Version: Preliminary
Preliminary
TS4268
180mA Ultra Low Dropout Voltage Regulator
with Reset & Watchdog Function
Test Circuit
Reset Timing
The power-on reset delay time is defined by charging time of an external capacitor C
D
which can be calculated as
follow:
C
D
= (
∆t
rd
x I
D,C
) /
∆V
Definitions:
C
D
= delay capacitor
∆t
rd
= delay time
I
D,C
= charge current, typical 12uA
∆V
= V
DU
, typical 1.8 V
V
DU
= upper delay switching threshold at C
D
for reset delay time
The reset reaction time trr is the time it takes the voltage regulator to set the reset out LOW after the output voltage has
dropped below the reset threshold. It is typically 1uS for delay capacitor of 47nF. For other values for C
D
the reaction
time can be estimated using the following equation:
Trr
≈
20 s/F x C
D
5/7
Version: Preliminary
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