NCP1031 ON, NCP1031 Datasheet - Page 13

• Manufacturer Part Number: NCP1031
• Description: Low Power PWM Controller with On-Chip Power Switch and Startup Circuits for 48V Telecom Systems
• Manufacturer: ON

Introduction
monolithic voltage−mode switching regulators designed for
isolated and non−isolated bias supply applications. The
internal startup circuit and the MOSFET are rated at 200 V,
making them ideal for 48 V telecom and 42 V automotive
applications. In addition, the NCP103x family can operate
from an existing 12 V supply. This controller family is
optimized for operation up to 1 MHz.
active power, control logic and protection circuitry required
to implement, with a minimum of external components,
several switching regulator applications, such as a
secondary side bias supply or a low power dc−dc converter.
package and is targeted for applications requiring up to 3 W.
The NCP1031 is targeted for applications up to 6 W and is
available in the SO−8 package.
including over temperature protection, cycle by cycle
current limit, individual line under and overvoltage
detection comparators with hysteresis, and regulator output
undervoltage lockout with hysteresis, providing full
protection during fault conditions. A description of each of
the functional blocks is given below, and the representative
block diagram is shown in Figure 2.
Startup Circuit and Undervoltage Lockout
that eliminates the need for external startup components.
The startup regulator consists of a constant current source
that supplies current from the input line (V
on the V
approximately 10 V, the startup circuit is disabled and the
Power Switch Circuit is enabled if no faults are present.
During this self−bias mode, power to the NCP103x is
supplied by the V
ON again once V
operation is known as Dynamic Self Supply (DSS). The
NCP1030 and NCP1031 startup currents are 12 mA and 16
mA, respectively.
While in the re−start mode, the V
discharge to 6.5 V while the Power Switch is enabled. Once
the 6.5 V threshold is reached, the Power Switch Circuit is
disabled and the startup regulator is enabled to charge the
V
V
capacitor must be sized such that a voltage greater than 7.5
V is maintained on the V
output reaches regulation. Otherwise, the converter will
enter the re−start mode. Equation (1) provides a guideline
for the selection of the V
converter;
CC
CC
The NCP1030 and NCP1031 are a family of miniature
The NCP103x family incorporates in a single IC all the
The NCP1030 is available in the space saving Micro8t
The NCP103x includes an extensive set of features
The NCP103x contains an internal 200 V startup regulator
If V
capacitor. The Power Switch is enabled again once the
voltage reaches 10 V. Therefore, the external V
CC
falls below 7.5 V, the device enters a re−start mode.
CC
pin (C
CC
CC
CC
reaches 7.5 V. This “7.5−10” mode of
capacitor. The startup regulator turns
). Once the V
CC
CC
capacitor while the converter
CC
capacitor for a forward
capacitor is allowed to
CC
in
) to the capacitor
voltage reaches
OPERATING DESCRIPTION
NCP1030, NCP1031
http://onsemi.com
CC
13
C CC +
where, I
including the IC bias current (I
current used to bias the feedback resistors (if used).
V
startup regulator from turning ON and reduce power
dissipation. Also, the load should not be directly connected
to the V
startup circuit. Figure 33 shows the recommended
configuration for a non−isolated flyback converter.
200 V. Power dissipation should be observed to avoid
exceeding the maximum power dissipation of the package.
Error Amplifier
voltage of the bias supply. It compares a scaled output
voltage signal to an internal 2.5 V reference (V
connected to its non−inverting input. The scaled signal is fed
into the feedback pin (
error amplifier.
compensation and connection to the PWM comparator
through the COMP pin. To insure normal operation, the EA
compensation should be selected such that the EA frequency
response crosses 0 dB below 80 kHz.
over the operating range. The output source and sink
currents are typically 110 mA and 550 mA, respectively.
move from the bottom to the top of the C
current is required to complete the COMP swing if small
resistors or large capacitors are used to implement the
compensation network. In which case, the COMP swing will
V
+
−
CC(off)
Figure 33. Non−Isolated Bias Supply Configuration
Forward:
After initial startup, the V
The maximum voltage rating of the startup circuit is
The internal error amplifier (EA) regulates the output
The output of the error amplifier is available for frequency
The error amplifier input bias current is less than 1 mA
Under load transient conditions, COMP may need to
in
bias
CC
cos
using an auxiliary winding. This will prevent the
capacitor. Otherwise, the load may override the
is the bias current supplied by the V
−1
GND
C
V
COMP
NCP103x
FB
T
1 *
V
DC@V in @N S
V
DRAIN
V OUT@ N P
CC
UV
OV
V
FB
) which is the inverting input of the
2.6
CC
pin should be biased above
L
CC1
OUT
) and any additional
C
OUT
T
@ I bias
Ramp. A large
CC
V
capacitor
+
−
out
(eq. 1)
REF
)