OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

PIP250M,518

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P19
Philips Semiconductors
PIP250M
Integrated buck converter
Product data Rev. 02 — 21 February 2003 4 of 19
9397 750 10904
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
[1] PAD1, PAD2 and PAD3 are electrical connections and must be soldered to the printed circuit board
[2] All n.c. pins should be connected to V
SSC
.
7. Functional description
7.1 Pin functions
7.1.1 Output stage supply (V
DDO
, V
SSO
)
The power output stage of the PIP250M consists of two N-channel, power MOSFETs
and a Schottky diode configured as a synchronous buck converter. The drain of the
upper MOSFET is connected to the positive conversion supply (V
DDO
), and the
source of the lower MOSFET is connected to power ground (V
SSO
). The Schottky
diode is connected between the source and drain of the lower MOSFET.
7.1.2 Output voltage (VO)
VO is the switched node of the power MOSFET output stage. This node is connected
internally to the source of the upper MOSFET and the drain of the lower MOSFET.
7.1.3 Control circuit supply (V
DDC
, V
SSC
)
V
DDC
is the positive supply to the control circuit. V
SSC
is the control circuit ground. All
control voltages are measured with respect to V
SSC
.
7.1.4 Bootstrap capacitor connection (CB)
The upper MOSFET driver stage is powered from the CB pin.
7.1.5 Voltage feedback pin (FB)
The FB pin is connected to the inverting input of the error amplifier, and to the inputs
of the overvoltage and undervoltage comparators.
7.1.6 Current limit set and enable input (OCSET/ENABLE)
The overcurrent threshold is set by an external resistor between V
DDO
and
OCSET/ENABLE. The PIP250M can be shut down by pulling this pin LOW.
7.1.7 Sense connection for current limit (PHASE)
The PHASE input is normally connected externally to the power output stage
switched node (VO). The voltage on the PHASE input is compared with the voltage
on the OCSET/ENABLE input during the interval when the upper MOSFET is on. The
overcurrent trip operates if the voltage on the PHASE input is lower than the voltage
on the OCSET/ENABLE input.
Philips Semiconductors
PIP250M
Integrated buck converter
Product data Rev. 02 — 21 February 2003 5 of 19
9397 750 10904
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
7.2 Operation
7.2.1 Single supply operation
Operation of the PIP250M from a single 5 V conversion supply is shown in Figure 3.
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
DDO
.
The control circuit supply, V
DDC
is protected from transients by a low pass filter
comprising a 10 Ω resistor and a 1 µF capacitor. These components should be
placed close to the device pins.
7.2.2 Regulated output voltage
The reference voltage of the PIP250M is 0.8 V. The regulated output voltage is set
using a resistive divider as shown in Figure 9. The resistors should be placed as
close as possible to the FB pin. Both resistors should be less than 1 kΩ 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.
7.2.3 Power on reset
The PIP250M control circuit powers up when the voltage on V
DDC
rises above the
start-up threshold voltage (typically 4.1 V). The control circuit stops operating when
the voltage on V
DDC
falls below the power-down threshold voltage (typically 3.6 V).
Once the voltage on V
DDC
is above the start-up threshold voltage, the PIP250M does
not produce pulses until the voltage on OCSET/ENABLE rises above the OCSET/
ENABLE start-up threshold voltage (typically 1.25 V).
7.2.4 Soft start
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.
03ak42
10 Ω
1 µF
100
µF
100 nF
5 V
CB
V
DDC
V
DDO
V
SSO
V
SSC
VO
D1
PIP250M
Philips Semiconductors
PIP250M
Integrated buck converter
Product data Rev. 02 — 21 February 2003 6 of 19
9397 750 10904
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
7.2.5 Overcurrent protection
The overcurrent protection function is shown in Figure 4. The overcurrent trip function
is enabled when the upper MOSFET gate drive signal is HIGH.
During this interval, the voltage on the PHASE input is compared with the voltage on
the OCSET/ENABLE input. If the voltage on the PHASE input is lower than the
voltage on the OCSET/ENABLE input, then the PIP250M detects an overcurrent trip
condition and turns off the gate drive to the upper MOSFET. There is an internal filter
with a time constant of 30 µs in series with the PHASE input. Since the switching
frequency is 300 kHz, this means that the overcurrent trip operates if the overcurrent
condition persists for10 switching cycles.
If three overcurrent pulses are detected, the PIP250M latches off and produces no
more pulses until it has been reset. To reset the PIP250M, the supply voltage (V
DDC
)
must be reduced below the power down reset threshold and then increased back up
to 5 V.
An external resistor (R
OCSET
) sets the overcurrent trip level. Figure 5 shows the
overcurrent trip level (I
TRIP
) as a function of R
OCSET
.
Fig 4. Overcurrent protection.
OC
R
OCSET
1 nF
03ak44
CONTROL
LOGIC
40 µA
5 V
VO
V
DDO
OCSET/
ENABLE
PHASE
PIP250M
strobe
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P19

PIP250M,518

Mfr. #:
Buy PIP250M,518
Manufacturer:
NXP Semiconductors
Description:
IC REG BUCK ADJ 15A 68HVQFN
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet