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PDF SEA05 Data sheet ( Hoja de datos )
| Número de pieza | SEA05 | |
| Descripción | Advanced constant voltage and constant current controller | |
| Fabricantes | ST Microelectronics | |
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SEA05
Advanced constant voltage and constant current controller
Features
■ Constant voltage and constant current control
■ Wide operating VCC range [3.5 - 36] V
■ Low quiescent consumption: 200 µA
■ Voltage reference: 2.5 V
■ Voltage control loop accuracy +/- 0.5%
■ Current sense threshold: 50 mV
■ Open-drain output stage
■ Low external component count
■ SOT23-6L micro package
Applications
■ Battery chargers
■ AC-DC adapters
■ LED drivers
Description
The SEA05 is a highly integrated solution for
SMPS applications requiring a dual control loop to
perform CV (constant voltage) and CC (constant
current) regulation.
The device integrates a voltage reference, two op-
amps (with OR-ed open-drain outputs), and a low-
side current sensing circuit.
The voltage reference, along with one op-amp, is
the core of the voltage control loop; the current
sensing circuit and the other op-amp make up the
current control loop.
The external components needed to complete the
two control loops are: a resistor divider that
senses the output of the power supply and fixes
the voltage regulation setpoint at the specified
value; a sense resistor that feeds the current
sensing circuit with a voltage proportional to the
dc output current; this resistor determines the
current regulation setpoint and must be
SOT23 - 6L
adequately rated in terms of power dissipation;
the frequency compensation components (R-C
networks) for both loops.
The device, housed in one of the smallest
available package, is ideal for space-shrunk
applications such as adapters and chargers.
Figure 1.
Internal schematic
2.5 V
Vcc
6
1.23 V
+
-
5
3
Out
Vctrl
+
- 2 Gnd
41
Ictrl Isense
Table 1. Device summary
Order code
Package
SEA05TR
SOT23-6L
Packing
Tape and reel
April 2010
Doc ID 17014 Rev 1
1/10
www.st.com
10
1 page  
SEA05
5 Application information
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Application information
Note:
Figure 4. Application information
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A 15 Ω resistor in series to Ictrl pin helps to protect the IC in case of negative voltage that
exceed the AMR of Ictrl pin.
As example a potential dangerous phenomenon could happen during converter output
short-circuit.
Consider the steady state operation of the circuit during voltage mode regulation (i.e. the
output is at its nominal voltage). The output capacitor is fully charged at Vo. If an abrupt
short (i.e. with negligible impedance) is applied at the output, instantly the positive pin of the
electrolytic capacitor is connected to the SEA05 ground. Since the capacitor acts like a
battery, all its voltage is applied across the Rsense pin and therefore the Ictrl pin is pulled
down to –Vo. This could damage the IC in case the Ictrl pin AMR is violated.
In reality the short is not so severe because it has a some impedance, the electrolytic
capacitor has an ESR and it starts discharging as soon as the short is applied. The Ictrl pin
is brought to a negative voltage anyway. The pin internal structure has been design to be
robust against negative voltage but, since the severity of this phenomenon is proportional to
the output voltage, for some applications an external resistor in series with Ictrl pin helps
protect the IC.
The resistor added in series with Ictrl pin introduces an error in the current sense threshold
voltage.
This error can be calculated considering the Ictrl pin current: this current multiplied by the
value of the external resistor gives the current sense threshold variation.
As example if we add a 15 Ω resistor in series to Ictrl pin, we have
Ictrl current = Ibias = 6 µA and therefore the error
6 µA x 15 Ω = 80 µV, the error is 80 µV / 50 mV = 0.16%
Doc ID 17014 Rev 1
5/10
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet SEA05.PDF ] | |
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