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PDF CS5156GN16 Data sheet ( Hoja de datos )
| Número de pieza | CS5156GN16 | |
| Descripción | CPU 5-Bit Nonsynchronous Buck Controller | |
| Fabricantes | Cherry Semiconductor Corporation | |
| Logotipo |  |
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CS5156
CPU 5-Bit Nonsynchronous Buck Controller
Description
Features
The CS5156 is a 5-bit nonsyn-
chronous N-Channel buck con-
troller. It is designed to provide
unprecedented transient response
for today’s demanding high-densi-
ty, high-speed logic. The regulator
operates using a proprietary control
method, which allows a 100ns
response time to load transients.
The CS5156 is designed to operate
over a 4.25-16V range (VCC) using
12V to power the IC and 5V as the
main supply for conversion.
The CS5156 is specifically designed
to power Pentium® II processors
and other high performance core
logic. It includes the following fea-
tures: on board, 5-bit DAC, short
circuit protection, 1.0% output tol-
erance, VCC monitor, and pro-
grammable soft start capability. The
CS5156 is backwards compatible
with the 4-bit CS5151, allowing the
mother board designer the capabili-
ty of using either the CS5151 or the
CS5156 with no change in layout.
The CS5156 is available in 16 pin
surface mount and DIP packages.
Application Diagram
Switching Power Supply for core logic - Pentium® II processor
12V 5V
VID0
VID1
VID2
VID3
VID4
330pF
0.1µF
1200µF/16V x 3
AlEl
VCC1 VCC2
VGATE
VID0
VID1
VID2
VID3
VID4
CS5156
COFF
PGnd
IRL3103
2µH
2
MBR1535CT
1,3
1.3V to 3.5V @ 13A
1200µF/16V x 5
AlEl
0.1µF
SS
COMP
0.33µF
LGnd
VFB
VFFB
3.3k
100pF
V2 is a trademark of Switch Power, Inc.
Pentium is a registered trademark of Intel Corporation.
s N-Channel Design
s Excess of 1MHz Operation
s 100ns Transient Response
s 5-Bit DAC
s Backward Compatible with
4-Bit CS5150/5151 and
Adjustable CS5120/5121
s 30ns Gate Rise/Fall Times
s 1% DAC Accuracy
s 5V & 12V Operation
s Remote Sense
s Programmable Soft Start
s Lossless Short Circuit
Protection
s VCC Monitor
s Adaptive Voltage
Positioning
s V2™ Control Topology
s Current Sharing
s Overvoltage Protection
Package Options
16 Lead SO Narrow & PDIP
VID0 1
VID1
VID2
VID3
SS
VID4
COFF
VFFB
VFB
COMP
LGnd
VCC1
NC
PGnd
VGATE
VCC2
Rev. 1/5/99
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: [email protected]
Web Site: www.cherry-semi.com
1 A ® Company
1 page  
PACKAGE PIN #
16L SO Narrow & PDIP
11
12
13
14
15
16
Package Pin Description: continued
PIN SYMBOL
FUNCTION
PGnd
NC
VCC1
LGnd
COMP
VFB
High current ground for the IC. The MOSFET driver is referenced to
this pin. Input capacitor ground and the anode of the Schottky diode
should be tied to this pin.
No connection.
Input power for the IC.
Signal ground for the IC. All control circuits are referenced to this pin.
Error amplifier compensation pin. A capacitor to ground should be
provided externally to compensate the amplifier.
Error amplifier DC feedback input. This is the master voltage feedback
which sets the output voltage. This pin can be connected directly to the
output or a remote sense trace.
Block Diagram
VCC1
SS
VID0
VID1
VID2
VID3
VID4
VFB
COMP
VFFB
LGnd
VCC1 Monitor
Comparator
-
+
3.90V
3.85V
5V
60µA
2µA
5 BIT
DAC
Error
+ Amplifier
-
Slow Feedback
PWM
Comparator
-
+
Fast Feedback
-
+
VFFB Low
1V Comparator
PWM
COMP
2.5V
SS Low
- Comparator
+
0.7V
SS High
+ Comparator
-
FAULT
RQ
S Q FAULT
FAULT
Latch
Maximum
On-Time
Timeout
Normal
Off-Time
Timeout
Extended
Off-Time
Timeout
RQ
SQ
PWM
Latch
Off-Time
Timeout
GATE = ON
GATE = OFF
COFF
One Shot
R
SQ
Time Out
Timer
(30µs)
Edge Triggered
VCC2
VGATE
PGnd
COFF
5
5 Page 
Applications Information: continued
Channel 3 = VGATE
M1= VGATE - 5VIN
Channel 2 = Inductor Switching Node
Figure 15: CS5156 gate drive waveforms depicting rail to rail swing.
The most important aspect of MOSFET performance is
RDSON, which effects regulator efficiency and MOSFET
thermal management requirements.
The power dissipated by the MOSFETs and the Schottky
diode may be estimated as follows;
Switching MOSFET:
Power = ILOAD2 × RDSON × duty cycle
Schottky diode:
Power = VFORWARD × ILOAD × (1 - duty cycle)
Duty Cycle =
VOUT + VFORWARD
VIN + VFORWARD - (ILOAD × RDSON OF SWITCH FET)
Off Time Capacitor (COFF)
The COFF timing capacitor sets the regulator off time:
TOFF = COFF × 4848.5
When the VFFB pin is less than 1V, the current charging the
COFF capacitor is reduced. The extended off time can be cal-
culated as follows:
TOFF = COFF × 24,242.5.
Off time will be determined by either the TOFF time, or the
time out timer, whichever is longer.
The preceding equations for duty cycle can also be used to
calculate the regulator switching frequency and select the
COFF timing capacitor:
COFF
=
Period × (1 - duty cycle)
4848.5
,
where:
Period =
1
switching frequency
“Droop” Resistor for Adaptive Voltage Positioning
Adaptive voltage positioning is used to reduce output volt-
age excursions during abrupt changes in load current.
Regulator output voltage is offset +40mV when the regula-
tor is unloaded, and -40mV at full load. This results in
increased margin before encountering minimum and maxi-
mum transient voltage limits, allowing use of less capaci-
tance on the regulator output (see Figure 7).
To implement adaptive voltage positioning, a “droop”
resistor must be connected between the output inductor
and output capacitors and load. This is normally imple-
mented by a PC board trace of the following value:
80mV
RDROOP = IMAX
Adaptive voltage positioning can be disabled for improved
DC regulation by connecting the VFB pin directly to the load
using a separate, non-load current carrying circuit trace.
Input and Output Capacitors
These components must be selected and placed carefully to
yield optimal results. Capacitors should be chosen to pro-
vide acceptable ripple on the input supply lines and regula-
tor output voltage. Key specifications for input capacitors
are their ripple rating, while ESR is important for output
capacitors. For best transient response, a combination of
low value/high frequency and bulk capacitors placed close
to the load will be required.
Output Inductor
The inductor should be selected based on its inductance,
current capability, and DC resistance. Increasing the induc-
tor value will decrease output voltage ripple, but degrade
transient response.
Thermal Management
Thermal Considerations for Power MOSFETs and Diodes
In order to maintain good reliability, the junction tempera-
ture of the semiconductor components should be kept to a
maximum of 150°C or lower. The thermal impedance (junc-
tion to ambient) required to meet this requirement can be
calculated as follows:
Thermal Impedance =
TJUNCTION(MAX) - TAMBIENT
Power
A heatsink may be added to TO-220 components to reduce
their thermal impedance. A number of PC board layout
techniques such as thermal vias and additional copper foil
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet CS5156GN16.PDF ] | |
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