NCP5500(2006) 데이터 시트보기 (PDF) - ON Semiconductor
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NCP5500 Datasheet PDF : 9 Pages
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NCP5500, NCV5500, NCP5501, NCV5501
Input
IIN
CBulk
10 mF
Enable
IEN
CIN
100 nF
IN
OUT
NCV5500 NCP5500
EN
ADJ
GND
IGND
IQ
IOUT
COUT
Output
RL
IADJ
Input
IIN
CBulk
10 mF
CIN
100 nF
IN
NCV5501
OUT
GND
IGND
IQ
IOUT
COUT
Output
RL
Figure 3. Measuring Circuits
Circuit Description
The NCP5500/NCP5501/NCV5500/NCV5501 are
integrated linear regulators with a DC load current
capability of 500 mA. The output voltage is regulated by a
PNP pass transistor controlled by an error amplifier and
band gap reference. The choice of a PNP pass element
provides the lowest possible dropout voltage, particularly at
reduced load currents. Pass transistor base drive current is
controlled to prevent oversaturation. The regulator is
internally protected by both current limit and thermal
shutdown. Thermal shutdown occurs when the junction
temperature exceeds 150°C. The NCV5500 includes an
enable/shutdown pin to turn off the regulator to a low current
drain standby state.
Regulator
The error amplifier compares the reference voltage to a
sample of the output voltage (VOUT) and drives the base of
a PNP series pass transistor via a buffer. The reference is a
bandgap design for enhanced temperature stability.
Saturation control of the PNP pass transistor is a function of
the load current and input voltage. Oversaturation of the
output power device is prevented, and quiescent current in
the ground pin is minimized.
Regulator Stability Considerations
The input capacitors (CBULK and CIN) are necessary to
stabilize the input impedance to reduce transient line
influences. The output capacitor helps determine three main
characteristics of a linear regulator: startup delay, load
transient response and loop stability. The capacitor value
and type should be based on cost, availability, size and
temperature constraints. A tantalum or aluminum
electrolytic capacitor is best, since a film or ceramic
capacitor with its almost zero ESR, can cause instability. The
aluminum electrolytic capacitor is the least expensive
solution. However, if the circuit operates at low
temperatures (−25°C to −40°C), both capacitor value and
ESR will vary considerably. The capacitor manufacturer’s
data sheet usually provides temperature performance data.
Stability is guaranteed for COUT = 4.7 mF and ESR < 3 W.
Enable Input (NCP5500, NCV5500)
The enable pin is used to turn the regulator on or off. By
holding the pin at a voltage less than 0.5 V, the output of the
regulator will be turned off to a minimal current drain state.
When the voltage at the Enable pin is greater than 2.0 V, the
output of the regulator will be enabled and rise to the
regulated output voltage. The Enable pin may be connected
directly to the input pin to provide a constant enable to the
regulator.
Active Load Protection in Shutdown
(NCP5500, NCV5500)
When a linear regulator is disabled (shutdown), the output
(load) voltage should be zero. However, stray PC board
leakage paths, output capacitor dielectric absorption, and
inductively coupled power sources can cause an undesirable
regulator output voltage if load current is low or zero. The
NCV5500 features a load protection network that is active
only during Shutdown mode. This network switches in a
shunt current path (~500 mA) from VOUT to Ground. This
feature also provides a controlled (“soft”) discharge path for
the output capacitor after a transition from Enable to
Shutdown.
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