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PDF L4989D Data sheet ( Hoja de datos )
| Número de pieza | L4989D | |
| Descripción | Low power voltage regulator | |
| Fabricantes | STMicroelectronics | |
| Logotipo |  |
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L4989D
L4989MD
Low power voltage regulator
Features
■ Operating DC supply voltage range 5.6 V to
31 V
■ Very low quiescent current with watchdog
disabled
■ Precision output voltage (3%)
■ Low drop voltage (180 mV typ at Io = 150 mA)
■ Reset circuit sensing the output voltage down
to 1 V
■ Programmable reset delay with external
capacitor
■ Watchdog disable input
■ Programmable watchdog timer with external
capacitor
■ Thermal shutdown and short circuit protection
■ Wide temperature range (Tj = -40°C to 150°C)
Datasheet production data
SO-8
SO-20
Description
The L4989M and L4989MD are monolithic
integrated 5 V voltage regulators with a low drop
voltage at currents up to 150 mA.
The output voltage regulating element consists in
a p-channel MOS and the regulation is performed
regardless of input voltage transients up to 40 V.
The high precision of the output voltage is
obtained with a pre-trimmed reference voltage.
The devices are protected against short circuit
and an overtemperature protection switches off
the devices in case of extremely high power
dissipation.
The L4989M and L4989MD watchdogs are active
when the Enable pin is high. Features like reset
and watchdog make this devices particularly
suitable to supply microprocessor systems in
automotive applications.
Table 1. Device summary
Package
SO-8
SO-20
Tube
L4989D
L4989MD
Order codes
Tape and reel
L4989D013TR
L4989MD013TR
September 2013
This is information on a product in full production.
Doc ID 022376 Rev. 2
1/19
www.st.com
1
1 page  
L4989D, L4989MD
Block diagram and pin configuration
1 Block diagram and pin configuration
Figure 1. Block diagram
Table 2. Pins description
Pin name SO-8(D)
S0-20(MD)
Function
WEn
Gnd
Gnd
Res
Vcr
Vcw
Wi
Watchdog Enable input
11
If high watchdog functionality is active
2 4 Ground reference
Ground.
5, 6, 15, 16
Connected these pins to a heat spreader ground
Reset output.
3 7 It is pulled down when output voltage goes below Vo_th
or frequency at Wi is too low.
Reset timing adjust.
4 10 A capacitor between Vcr pin and gnd, sets the reset
delay time (trd)
Watchdog timer adjust
5 11 A capacitor between Vcw pin and gnd, sets the time
response of the watchdog monitor.
Watchdog input.
6 14 If the frequency at this input pin is too low, the Reset
output is activated.
Doc ID 022376 Rev. 2
5/19
5 Page 
L4989D, L4989MD
3 Application information
Application information
3.1 Voltage regulator
The voltage regulator uses a p-channel MOS transistor as a regulating element. With this
structure a very low dropout voltage at current up to 150 mA is obtained. The output voltage
is regulated up to transient input supply voltage of 40 V. No functional interruption due to
over-voltage pulses is generated.The voltage Regulator is always active and not depending
on the state of WEn input pin. A short circuit protection to GND is provided.
Figure 3. Behavior of output current versus regulated voltage Vo
Vo
Vo_ref
Ishort Ilim Iout
3.2
Reset
The reset circuit supervises the output voltage Vo. The Vo_th reset threshold is defined with
the in-ternal reference voltage and a resistor output divider. If the output voltage becomes
lower than Vo_th then Res goes low with a reaction time trr. The reset low signal is
guaranteed for an output voltage Vo greater than 1 V.
When the output voltage becomes higher than Vo_th then Res goes high with a delay trd.
This delay is obtained by an internal oscillator.
The oscillator period is given by:
Tosc = [(Vrhth - Vrlth) x Ctr] / Icr + [(Vrhth - Vrlth) x Ctr] / Idr
where:
Icr:
Idr:
Vrhth, Vrlth:
is an internally generated charge current
is an internally generated discharge current
are two voltages defined with the output voltage and a resistor output
divider
Ctr: is an external capacitance.
trd is given by:
trd = 512 x Tosc
The Reset is always active and not depending on the state of WEn input pin.
Doc ID 022376 Rev. 2
11/19
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet L4989D.PDF ] | |
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