LM2633
Advanced Two-Phase Synchronous Triple Regulator
Controller for Notebook CPUs
General Description
The LM2633 is a feature-rich IC that combines three regu-
lator controllers - two current mode synchronous buck regu-
lator controllers and a linear regulator controller.
The two switching regulator controllers operate 180 out of
phase. This feature reduces the input ripple RMS current,
resulting in a smaller input filter.
The first switching controller (Channel 1) features an Intel
mobile CPU compatible precision 5-bit digital-to-analog con-
verter which programs the output voltage from 0.925V to
2.00V. It is also compatible with the dynamic VID require-
ments. The second switching controller (Channel 2) is ad-
justable between 1.25V to 6.0V.
Use of synchronous rectification and pulse-skip operation at
light load achieves high efficiency over a wide load range.
Fixed-frequency operation can be obtained by disabling the
pulse-skip mode.
Current-mode feedback control assures excellent line and
load regulation and a wide loop bandwidth for good re-
sponse to fast load transient events. Current mode control is
achieved through sensing the Vds of the top FET and thus
an external sense resistor is not necessary.
A power good signal is available to indicate the general
health of the output voltages.
A unique feature is the analog soft-start for the switching
controllers is independent of the slew rate of the input volt-
age. This will make the soft start behavior more predictable
and controllable. An internal 5V rail is available externally for
boot-strap circuitry (only) when no 5V is available from other
sources.
Current limit for either of the two switching channels is
achieved through sensing the top FET V
and the value is
adjustable. The two switching controllers have under-voltage
and over-voltage latch protections, and the linear regulator
has under-voltage latch protection. Under-voltage latch can
be disabled or delayed by a programmable amount of time.
The input voltage for the switching channels ranges from 5V
to 30V, which makes possible the choice of different battery
chemistries and options.
Features
GENERAL
n
Three regulated output voltages
n
4.5V to 30V input range
n
Power good function
n
Input under-voltage lockout
n
Thermal shutdown
n
Tiny TSSOP package
SWITCHING SECTION
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Two channels operating 180 out of phase
n
Separate on/off control for each channel
n
Current mode control without sense resistor
n
Skip-mode operation available
n
Adjustable cycle-by-cycle current limit
n
Negative current limit
n
Analog soft start independent of input voltage slew rate
n
Power ground pins separate
n
Output UVP and OVP
n
Programmable output UVP delay
n
250kHz switching frequency (for Vin
<
17V)
n
Channel 1 output from 0.925V to 2.00V
n
±
1.5% DAC accuracy from 0C to 125C
n
±
1.7% initial tolerance for Channel 2
n
Dynamic VID change ready
n
Power good flags VID changes
n
Channel 2 output from 1.3V to 6.0V
LINEAR SECTION
n
Output voltage adjustable
n
50mA maximum driving current
n
Output UVP
n
±
2% initial tolerance
Applications
n
Power supply for CPUs of notebook PCs that require
the SpeedStep
technique
n
Power supply for information appliances
n
General low voltage DC/DC buck regulators
SpeedStep
is a trademark of Intel Corporation.
August 2001
L
2001 National Semiconductor Corporation
DS200008
www.national.com