pip250m NXP Semiconductors, pip250m Datasheet - Page 5

• Manufacturer Part Number: pip250m
• Description: Pip250m Integrated Buck Converter
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 10904
Product data
7.2.1 Single supply operation
7.2.2 Regulated output voltage
7.2.3 Power on reset
7.2.4 Soft start
7.2 Operation
Operation of the PIP250M from a single 5 V conversion supply is shown in
The upper MOSFET gate driver stage is supplied from the CB pin. An external
bootstrap circuit, comprising D1 and the 100 nF capacitor generates a voltage on CB
of twice V
The control circuit supply, V
comprising a 10
placed close to the device pins.
The reference voltage of the PIP250M is 0.8 V. The regulated output voltage is set
using a resistive divider as shown in
close as possible to the FB pin. Both resistors should be less than 1 k in order to
avoid noise coupling. The 68 nF capacitor across the upper resistor improves the
control loop stability by adding a small amount of phase margin.
The PIP250M control circuit powers up when the voltage on V
start-up threshold voltage (typically 4.1 V). The control circuit stops operating when
the voltage on V
Once the voltage on V
not produce pulses until the voltage on OCSET/ENABLE rises above the OCSET/
ENABLE start-up threshold voltage (typically 1.25 V).
The soft start sequence prevents surge currents being drawn from the conversion
supply when the PIP250M is powered up into a high current load. The soft start
sequence is controlled by an internal digital counter. During the soft start sequence,
the reference voltage on the non inverting input of the error amplifier is increased
from zero up to the normal operating level of 0.8 V. The duration of the soft start
sequence is typically 2 ms.
Fig 3. Single supply operation.
DDO
.
DDC
Rev. 02 — 21 February 2003
resistor and a 1 F capacitor. These components should be
falls below the power-down threshold voltage (typically 3.6 V).
DDC
1 F
V DDC
is above the start-up threshold voltage, the PIP250M does
DDC
V SSC
PIP250M
is protected from transients by a low pass filter
CB
10
Figure
V DDO
V SSO
9. The resistors should be placed as
VO
100 nF
D1
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
03ak42
Integrated buck converter
100
5 V
DDC
F
rises above the
PIP250M
Figure
5 of 19
3.