NCP1599
Product Preview
1 MHz, 3 A Synchronous
Buck Regulator
The NCP1599 is a fixed 1 MHz, high−output−current, synchronous
PWM converter that integrates a low−resistance, high−side P−channel
MOSFET and a low−side N−channel MOSFET. The NCP1599 utilizes
internally compensated current mode control to provide good transient
response, ease of implementation, and excellent loop stability. It
regulates input voltages from 2.8 V to 5.5 V down to an output voltage
as low as 0.8 V and is able to supply up to 3.0 A of load current.
The NCP1599 includes an internally fixed switching frequency
(F
SW
), and an internal soft−start to limit inrush current.
Other features include cycle−by−cycle current limiting,
short−circuit protection, power saving mode and thermal shutdown.
Features
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MARKING
DIAGRAM
1
DFN6
CASE 506AH
A
Y
WW
G
1
1599
AYWW
G
•
Wide Input Voltage Range: from 2.8 V to 5.5 V
•
Internal 140 mW High−Side P−Channel and 90 mW Low−Side
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
N−Channel MOSFET
Fixed 1 MHz Switching Frequency
Cycle−by−Cycle Current Limiting
Hiccup Mode Short−Circuit Protection
Overtemperature Protection
Internal Soft−Start
Start−up with Pre−Biased Output Load
Adjustable Output Voltage Down to 0.8 V
Power Saving Mode During Light Load
These are Pb−Free Devices
DSP Power
Hard Disk Drivers
Computer Peripherals
Home Audio
Set−Top Boxes
Networking Equipment
LCD TV
Wireless and DSL/Cable Modem
USB Power Devices
= Assembly Location
= Year
= Work Week
= Pb−Free Package
PIN CONNECTIONS
FB 1
GND 2
LX 3
(Top View)
6 COMP
5 VCC
4 VCCP
ORDERING INFORMATION
Device
NCP1599MNR2G
Package
Shipping
†
Applications
DFN6
3000 / Tape & Reel
(Pb−Free)
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
This document contains information on a product under development. ON Semiconductor
reserves the right to change or discontinue this product without notice.
©
Semiconductor Components Industries, LLC, 2010
May, 2010
−
Rev. P0
1
Publication Order Number:
NCP1599/D
NCP1599
min/max values unless noted otherwise)
Parameter
V
in
Input Voltage Range
V
CC
UVLO Threshold
UVLO Hysteresis
V
CC
Quiescent Current
V
CCP
Quiescent Current
FEEDBACK VOLTAGE
Reference Voltage
Feedback Input Bias Current
Feedback Voltage Line Regulation
GM AMPLIFIER
Gm Amp Open Loop Voltage Gain
(Note 2)
Gm Amp Transconductance (Note 2)
PWM
Maximum Duty Cycle (Regulating)
Minimum Controllable ON Time (Note 2)
CURRENT SENSE AMPLIFIER
Current Sense to COMP
Transconductance (Note 2)
PULSE−BY−PULSE CURRENT LIMIT
Pulse−by−Pulse Current Limit (Note 3)
OSCILLATOR
Oscillator Frequency
MOSFET
High Side MOSFET ON Resistance
High Side MOSFET Leakage (Note 2)
Low Side MOSFET ON Resistance
Low Side MOSFET Leakage (Note 2)
SOFT−START
Soft−Start Ramp Time (Note 2)
Hiccup Timer (Note 2)
THERMAL SHUTDOWN
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
2. Guaranteed by design.
3. Current limit operation not guaranteed below V
in
= 4.0 V.
170
40
°C
°C
t
SS
F
SW
= 1 MHz
1.0
2.0
ms
ms
R
DS(on)
HS
R
DS(on)
LS
I
DS
= 100 mA, V
GS
= 5 V
V
SW
= 0 V
I
DS
= 100 mA, V
GS
= 5 V
V
SW
= 5 V
90
140
200
10
125
10
mW
mA
mW
mA
F
SW
0.87
1.0
1.13
MHz
I
LIM
V
in
= 4.0 V
−
5.5 V
3.5
4.0
4.5
A
gm
POWER
5.0
A/V
83
50
%
ns
AV
gm
gm
COMP
V
FB
> 0.75 V,
DI
COMP
=$10
mA
55
1000
dB
mA/V
V
ref
I
FB
V
FB
= V
COMP
V
FB
= 0.8 V
V
FB
= V
COMP
, V
in
= 2.7 V to 6.0 V
0.788
0.800
10
0.812
100
0.03
V
nA
%/V
I
inVCC
I
inVCCP
V
in
= 5.0 V, V
FB
= 1.5 V, (No Switching)
V
in
= 5.0 V,V
FB
= 1.5 V, (No Switching)
ELECTRICAL CHARACTERISTICS
(V
in
= 2.8 V
−
5.5 V, V
out
= 1.2 V, T
J
= +25°C for typical value;
−40°C
< T
J
< +125°C for
Symbol
V
in
Test Conditions
Min
2.8
2.4
2.55
200
1.1
1.4
2.0
3.0
Typ
Max
5.5
2.65
Unit
V
V
mV
mA
mA
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4
NCP1599
DETAILED DESCRIPTION
Overview
Output MOSFETs
The NCP1599 is a synchronous PWM controller that
incorporates all the control and protection circuitry
necessary to satisfy a wide range of applications. The
NCP1599 employs current mode control to provide good
transient response, simple compensation, and excellent
stability. The features of the NCP1599 include a precision
reference, fixed 1 MHz switching frequency, a
transconductance error amplifier, an integrated high−side
P−channel MOSFET and low−side N−Channel MOSFET,
internal soft−start, and very low shutdown current. The
protection features of the NCP1599 include internal
soft−start, pulse−by−pulse current limit, hiccup mode
short−circuit protection, and thermal shutdown.
Reference Voltage
The NCP1599 includes low R
DS(on)
, both high−side
P−channel and low−side N−channel MOSFETs capable of
delivering up to 3.0 A of current. When the controller is
disabled or during a Fault condition, the controller’s output
stage is tri−stated by turning OFF both the upper and lower
MOSFETs.
Adaptive Dead Time Gate Driver
The NCP1599 incorporates an internal reference that
allows output voltages as low as 0.8 V. The tolerance of the
internal reference is guaranteed over the entire operating
temperature range of the controller. The reference voltage is
trimmed using a test configuration that accounts for error
amplifier offset and bias currents.
Oscillator Frequency
In a synchronous buck converter, a certain dead time is
required between the low side drive signal and high side
drive signal to avoid shoot through. During the dead time,
the body diode of the low side FET freewheels the current.
The body diode has much higher voltage drop than that of
the MOSFET, which reduces the efficiency significantly.
The longer the body diode conducts, the lower the
efficiency. In NCP1599, the drivers and MOSFETs are
integrated in a single chip. The parasitic inductance is
minimized. Adaptive dead time control method is used in
NCP1599 to prevent the shoot through from happening and
minimizing the diode conduction loss at the same time.
Pulse Width Modulation
A fixed precision oscillator is provided. The oscillator
frequency range is 1 MHz with
±13%
variation.
Transconductance Error Amplifier
The transconductance error amplifier’s primary function
is to regulate the converter’s output voltage using a resistor
divider connected from the converter’s output to the FB pin
of the controller, as shown in the applications Schematic. A
series RC compensation network must be connected from
the error amplifier’s output (COMP pin) to GND to stabilize
the converter. In some applications, a lower value capacitor
may be connected from the COMP pin to GND to reduce the
loop gain at higher frequencies. However, if this capacitor
is too large the phase margin of the converter will be
reduced. If a Fault occurs, the COMP pin is immediately
pulled to GND and PWM switching is inhibited.
Internal Soft−Start
A high−speed PWM comparator, capable of pulse widths
as low as 50 ns, is included in the NCP1599. The inverting
input of the comparator is connected to the output of the
error amplifier. The non−inverting input is connected to the
the current sense signal. At the beginning of each PWM
cycle, the CLK signal sets the PWM flip−flop and the upper
MOSFET is turned ON. When the current sense signal rises
above the error amplifier’s voltage then the comparator will
reset the PWM flip−flop and the upper MOSFET will be
turned OFF.
Power Save Mode
If the load current decreases, the converter will enter
power save mode operation automatically. During power
save mode, the converter skips switching and operates with
reduced frequency, which minimizes the quiescent current
and maintain high efficiency.
Current Sense Amplifier
To limit the startup inrush current, an internal soft start
circuit is used to ramp up the reference voltage from 0 V to
its final value linearly. The internal soft start time is 1 ms
typically.
The NCP1599 monitors the current in the upper
MOSFET. The current signal is required by the PWM
comparator, the pulse−by−pulse current limiter, and the
hiccup mode/over current counter.
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5
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