NSC LM2639M

LM2639
5-Bit Programmable, High Frequency Multi-phase PWM
Controller
General Description
The LM2639 provides an attractive solution for power supplies of high power microprocessors (such as Pentium II™,
M II™, K6™-2, K6™-3, etc.) exhibiting ultra fast load transients. Compared to a conventional single-phase supply, an
LM2639 based multi-phase supply distributes the thermal
and electrical loading among components in multiple phases
and greatly reduces the corresponding stress in each component. The LM2639 can be programmed to control either a
3-phase converter or a 4-phase converter. Phase shift
among the phases is 120˚ in the case of three phase and 90˚
with four-phase. Because the power channels are out of
phase, there can be significant ripple cancellation for both
the input and output current, resulting in reduced input and
output capacitor size. Due to the nominal operating frequency of 2 MHz per phase, the size of the output inductors
can be greatly reduced which results in a much faster load
transient response and a dramatically shrunk output capacitor bank. Microprocessor power supplies with all surface
mount components can be easily built.
The internal high speed transconductance amplifier guarantees good dynamic performance. The output drive voltages
can be adjusted through a resistor divider to control switching loss in the external FETs.
The internal master clock frequency of up to 8 MHz is set by
an external reference resistor. An external clock of 10 MHz
can also be used to drive the chip to achieve frequency control and multi-chip operation.
The LM2639 also provides input under-voltage lock-out with
hysteresis and input over-current protection.
Features
n
n
n
n
n
n
n
n
n
n
n
Ultra fast load transient response
Enables all surface-mount-design
Selectable 2, 3, 4 phase operation
Clock frequency from 40 kHz to 10 MHz
Precision load current sharing
5-bit programmable from 3.5V to 1.3V
VID code compatible to VRM 8.X specification
Output voltage is 2.0V for VID code 11111
Selectable internal or external clock
Digital 16-step soft start
Input under-voltage lock-out, over-current protection
Applications
n Servers and workstations
n High current, ultra-fast transient microprocessors
Pin Configuration
24-Pin Plastic SOIC
DS101143-1
Top View
See NS Package Number M24B
M II™ is a trademark of Cyrix Corporation a wholly owned subsidiary of National Semiconductor Corporation.
Pentium II™ is a trademark of Intel Corporation.
K6™ is a trademark of Advanced Micro Devices, Inc.
© 2000 National Semiconductor Corporation
DS101143
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LM2639 5-Bit Programmable, High Frequency Multi-phase PWM Controller
February 2000
LM2639
Absolute Maximum Ratings (Note 1)
Storage Temperature
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Susceptibility (Note 8)
VCC5V
7V
VCC12V
20V
Junction Temperature
2 kV
Soldering Time, Temperature
10 sec., 300˚C
Operating Ratings (Note 1)
VCC
125˚C
Power Dissipation (Note 2)
−65˚C to +150˚C
4.75V to 5.25V
Junction Temperature Range
0˚C to 70˚C
1.6W
Electrical Characteristics
VCC5V = 5V, VCC12V = 12V unless otherwise specified. Typicals and limits appearing in plain type apply for TA = TJ = +25˚C.
Limits appearing in boldface type apply over the entire operating temperature range.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
Vcc5V
VCC5V Pin Voltage
4.5
5.0
5.5
V
Vcc12V
VCC12V Pin Voltage
10.0
12.0
18.0
V
VDACOUT
5-bit DAC Output Voltage
ICC12V
Quiescent VCC12V Current
ICC5V
Operating VCC5V Current
VREF
Rref Pin Voltage
VINL
Vid0:4, Clksel, Divsel, and
Enable Pins Logic Threshold
VINH
IINL
Vid0:4 and Enable Pins Internal
Pullup Current
Clksel, Divsel Pins Internal
Pullup Current
(Note 3)
N
N+1%
N−1.5%
N
N+1.5%
1.3
3
mA
4.3
8
mA
1.5
V
Enable = 5V, VID = 00001,
DRV Outputs Floating
VOUT = 2.00V
1.225
Logic Low (Note 4)
Logic High (Note 5)
The Corresponding Pin = 0V
Gate Driver Resistance When
Sinking Current
ISINK = 50 µA, VCC12V = 14V
VDRV
DRV0:3 Output Voltage
IDRV = 10 mA, VCC12V = 14V,
OutV = 12V or 5V
tfall
DRV0:3 Fall Time
(Note 6)
ISRC
DRV0:3 Source Current
ISINK
DRV0:3 Sink Current
DRV0:3 = 0V, VCC12V = 14V,
OutV = 5V
DRV0:3 = 5V, VCC12V = 14V,
OutV = 5V
IFB
N−1%
1.8
2.8
60
100
140
−10
0
10
V
OutV
µA
Ω
12
OutV +
0. 3V
V
7
ns
40
60
mA
90
160
BgOUT Voltage
Current Limit Not Activated
4
0
FB Pin Bias Current
Current Limit Activated
FB = 2V
= 1V
V
3.5
OutV −
0.3V
V
250
mA
V
30
nA
BgOUT Sink Current
BgOUT
1.0
2.4
5
mA
FOSC
Oscillator Frequency
7.0
8.0
8.7
MHz
∆D
DRV0:3 Duty Cycle Match
8.02kΩ from Rref Pin to
Ground
Duty Cycle = 50%
−1
+1
%
∆ph
DRV0:3 Phase Accuracy
Duty Cycle = 50%, Fclock = 8
MHz
−1
+1
Deg
Toff
Toff
OutV
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PWM Off time
Drive Voltage Range
Divide by 4
22
Divide by 3
22
Output Freq. = 2MHz, VO =
2.00V
2
0
12
%
Vcc12
V
(Continued)
VCC5V = 5V, VCC12V = 12V unless otherwise specified. Typicals and limits appearing in plain type apply for TA = TJ = +25˚C.
Limits appearing in boldface type apply over the entire operating temperature range.
Symbol
Parameter
Conditions
VOCC_CM
Over-current Comparator
Common Mode Range
IB_OC+
OC+ Input Bias Current
IB_OC−
OC− Input Bias Current
VOS_OCC
Over-current Comparator Input
Offset Voltage
VIN = 5V, OC+ = 5V, OC− =
4V
VIN = 5V, OC+ = 6V, OC− =
5V
VIN = 5V
VIN = 12V
FB = 0V
Min
Typ
3
Max
Units
12
V
100
145
200
µA
85
125
165
µA
2
16
42
21
mV
78
%
1.36
mmho
2
V
DMAX
Maximun Duty Cycle
gm
Error Amplifier
Transconductance
Vramp
Ramp Signal Peak-to-Peak
Amplitude
Icomp
COMP Pin Source Current
250
400
550
µA
Icomp
COMP Pin Sink Current
160
280
400
µA
Vcomp_hi
COMP Pin High Clamp
2.9
V
Vcomp_lo
COMP Pin Low Clamp
0.19
V
VPOR
Power On Reset Trip Point
tSS
Vcc5V Pin Voltage Rising
4.0
Vcc5V Pin Voltage Falling
3.6
Vcc12V Minimum Working
Voltage
(Note 7)
3.8
V
Soft Start Delay
FOSC = 8MHz
1.6
ms
V
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating ratings do not imply guaranteed performance limits.
Note 2: Maximum allowable power dissipation is a function of the maximum junction temperature, TJMAX, the junction-to-ambient thermal resistance, θJA, and the
ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PMAX = (TJMAX − TA)/θJA. The
junction-to-ambient thermal resistance, θJA, for LM2639 is 78˚C/W. For a TJMAX of 150˚C and TA of 25˚C, the maximum allowable power dissipation is 1.6W.
Note 3: The letter N stands for the typical output voltages appearing in italic boldface type in Table 1.
Note 4: Max value of logic low means any voltage below this value is guaranteed to be taken as logic low whereas a voltage higher than this value is not guaranteed
to be taken as a logic low.
Note 5: Min value of logic high means any voltage above this value is guaranteed to be taken as logic high whereas a voltage lower than this value is not guaranteed
to be taken as a logic high.
Note 6: When driving bipolar FET drivers in the typical application circuit.
Note 7: When Vcc12V pin goes below this voltage, all DRV pins go to 0V.
Note 8: ESD ratings for pins DRV0, DRV1, DRV2 and DRV3 is 1kV. ESD rating for all other pins is 2kV.
3
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LM2639
Electrical Characteristics
LM2639
Electrical Characteristics
(Continued)
TABLE 1. 5-Bit DAC Output Voltage Table
Symbol
VDACOUT
Parameter
5-Bit DAC Output Voltages for Different VID Codes
Conditions
VID4:0 = 01111
VID4:0 = 01110
VID4:0 = 01101
VID4:0 = 01100
VID4:0 = 01011
VID4:0 = 01010
VID4:0 = 01001
VID4:0 = 01000
VID4:0 = 00111
VID4:0 = 00110
VID4:0 = 00101
VID4:0 = 00100
VID4:0 = 00011
VID4:0 = 00010
VID4:0 = 00001
VID4:0 = 00000
VID4:0 = 11111
VID4:0 = 11110
VID4:0 = 11101
4
Units
1.30
V
1.35
1.40
1.45
1.50
1.55
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.05
2.0
2.1
2.2
VID4:0 = 11100
VID4:0 = 11011
2.3
VID4:0 = 11010
VID4:0 = 11001
VID4:0 = 11000
2.5
VID4:0 = 10111
VID4:0 = 10110
VID4:0 = 10101
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Typical
2.4
2.6
2.7
2.8
2.9
3.0
VID4:0 = 10100
VID4:0 = 10011
VID4:0 = 10010
3.1
VID4:0 = 10001
VID4:0 = 10000
3.4
3.2
3.3
3.5
LM2639
Pin Description
Pin
Pin Name
Pin Function
1
Vcc5V
Supply Voltage Input (5V nominal)
2
Divsel
Selects Phase Mode. Logic low selects 4 phase. Logic high selects 3 phase. 2 phase
operation is achieved by using 2 outputs in 4 phase mode.
3
Clksel
4
Extclk
Clock Select: Logic high selects internal clock. Logic low selects external clock.
External Clock Input. Output frequency = Clock Input / No. of Phases. Connect to Vcc5V to
select internal clock.
5
Rref
Connects to external reference resistor. Sets the operating frequency of the internal clock
and the ramp time for the PWM. Reference voltage at this pin is 1.26V.
6
Vid0
5-Bit DAC Input (LSB).
7
Vid1
5-Bit DAC Input.
8
Vid2
5-Bit DAC Input.
9
Vid3
5-Bit DAC Input.
10
Vid4
5-Bit DAC Input (MSB)
11
OC+
Over-current Comparator. Non-inverting input.
12
OC−
Over-current Comparator. Inverting input.
13
COMP
Compensation Pin. This is the output of the internal transconductance amplifier.
Compensation network should be connected between this pin and feedback ground FBG.
14
FB
Feedback Input. Normally Kelvin connected to supply output.
15
Bgout
Current Limit Flag. Goes to logic low when current limit is activated. When over-current
condition is removed, this pin is weakly pulled up to Vcc5V.
16
FBG
Feedback Ground. This pin should be connected to the ground at the supply output.
17
ENABLE
Output Enable Pin. Tie to logic high to enable and logic low to disable.
18
GND
Power Ground Pin.
19
DRV2
Phase 2 Output.
20
DRV0
Phase 0 Output.
21
Vcc12V
Supply Voltage for FET Drivers DRV0:3.
22
DRV1
Phase 1 Output.
23
DRV3
Phase 3 Output.
24
OutV
Sets the maximum DRV0:3 drive voltage to reduce switching loss in external FET’s.
5
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DS101143-2
LM2639
Block Diagram
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6
LM2639
DS101143-3
Typical Application
7
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LM2639 5-Bit Programmable, High Frequency Multi-phase PWM Controller
Physical Dimensions
inches (millimeters) unless otherwise noted
24-Lead Small Outline Package
Order Number LM2639M
NS Package Number M24B
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