Page 1
UCC3830-4/-5/-6
02/99
FEATURES
• 5-Bit Digital-to-Analog Converter
(DAC)
• Supports 4-Bit and 5-Bit
Microprocessor VID Codes
• Combined DAC/Voltage Monitor
and PWM Functions
• 1% DAC/Reference
• Current Sharing
• 100kHz, 200kHz, 400kHz
Oscillator Frequency Options
• Foldback Current Limiting
• Overvoltage and Undervoltage
Fault Windows
• Undervoltage Lockout
• 4Ω Totem Pole Output
• Chip Disable Function
5-Bit Microprocessor Power Supply Controller
BLOCK DIAGRAM
UDG-96188-2
DESCRIPTION
The UCC3830-4/-5/-6 is a fully integrated single chip solution ideal for powering high performance microprocessors. The chip includes an average current
mode PWM controller, has a fully integrated 5-Bit DAC, and includes an
on-board precision reference and voltage monitor circuitry. The UCC3830-x
converts 5VDC to an adjustable output, ranging from 3.5VDC down to 1.8VDC
with 1% DC system accuracy (see Table 1). The UCC3830-x fully supports
Intel’s 4-bit Pentium® Pro and 5-bit Pentium® II VID codes.
The accuracy of the DAC/reference combination is 1%. The overvoltage and
undervoltage comparators monitor the system output voltage and indicate
when it rises above or falls below its programmed value by more than 8.5%. A
second overvoltage protection comparator pulls the current amplifier output
voltage low to force zero duty cycle when the system output voltage exceeds
its designed value by more than 17.5%. This comparator also terminates the
cycle. Undervoltage lockout circuitry assures the correct logic states at the
outputs during powerup and powerdown. The gate output can be disabled by
bringing the CAO/ENBL pin to below 0.8V.
(continued)
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2
UCC3830-4/-5/-6
CONNECTION DIAGRAM
SOIC-20 (Top View)
DW Package
ELECTRICAL CHARACTERISTICS:
Unless otherwise specified, VIN = 12V, VSENSE = 3.5V, VD0 = VD1 = VD2 = VD3 =
VD4 = 0V, 0°C < TA < 70°C, TA= TJ.
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
Undervoltage Lockout
VIN UVLO Turn-on Threshold 10.5 10.8 V
VIN UVLO Turn-off Threshold 9.5 10 V
UVLO Threshold Hysteresis 200 500 700 mV
Supply Current
l
IN D0 through D4 = Open 7.5 13.5 mA
DAC/Reference
COMMAND Voltage Accuracy 10.8V < VIN < 13.2V, I
VREF
= 0mA, 0°C < TA < 70°C –1 1 %
D0-D4 Voltage High DX Pin Floating 4 5 5.2 V
D0-D4 Input Bias Current DX Pin Tied to GND –100 –70 –20 µA
OVP Comparator
Trip Point % Over COMMAND Voltage (Note 1), D0 = D1 = D2 = D4
= Open, D3 = GND
10 17.5 25 %
Hysteresis 20 30 mV
VSENSE Input Bias Current OV, OVP, UV Combined –0.5 –0.1 0.5 µA
The voltage and current amplifiers have a 3MHz gain
bandwidth product to satisfy high performance system
requirements. The internal current sense amplifier permits the use of a low value current sense resistor, minimizing power loss. The oscillator frequency is fixed
internally at 100kHz, 200kHz, or 400kHz, depending
upon the option selected. The foldback circuit reduces
the converter short circuit current limit to 50% of its nominal value when the converter is short circuited. The gate
driver is a 4Ω totem pole output stage capable of driving
an external MOSFET.
This device is available in 20-pin dual in-line and surface
mount packages. The UCC3830-x is specified for operation from 0°C to 70°C.
Pentium®Pro and Pentium®Pro II are registered trademarks of
Intel Corporation.
DESCRIPTION (cont.)
FREQUENCY TABLE
Frequency
100kHz 200kHz 400kHz
UCC3830-4 X
UCC3830-5 X
UCC3830-6 X
UCC3830 –
ORDERING INFORMATION
Note: Consult factory for temperature range or package op-
tions not shown.
ABSOLUTE MAXIMUM RATING
Input Supply Voltage VIN . . . . . . . . . . . . . . . . . . . . . . . . . . 15V
D0, D1, D2, D3, D4, VSENSE, VFB, IS+, IS–, CAM Inputs
Maximum Forced Voltage. . . . . . . . . . . . . . . . –0.3V to 5.3V
PWRGOOD Output Maximum Voltage. . . . . . . . . . . . . . . . 5.5V
COMMAND Ouput Maximum Current . . . . . . Internally Limited
Reference Output Current . . . . . . . . . . . . . . . Internally Limited
Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Junction Temperature. . . . . . . . . . . . . . . . . . . –55°C to +150°C
Lead Temperature (Soldering, 10 sec.). . . . . . . . . . . . . +300°C
Currents are positive into negative out of the specified terminal.
Pulse is defined as a less than 10% duty cycle with a maximum
duration of 500 s. Consult Packaging Section of Databook for
thermal limitations and considerations of packages.
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3
UCC3830-4/-5/-6
ELECTRICAL CHARACTERISTICS: Unless otherwise specified, VIN = 12V, VSENSE = 3.5V, VD0 = VD1 = VD2 = VD3 =
VD4 = 0V, 0°C < TA < 70°C, TA= TJ.
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
OV Comparator
Trip Point % Over COMMAND Voltage (Note 1), D0 = D1 = D2 = D4
= Open, D3 = GND
5 8.5 12 %
Hysteresis 20 30 mV
PWRGOOD Equivalent Resistance VSENSE = 2.0V 470 Ω
UV Comparator
Trip Point % Over COMMAND Voltage (Note 1), D0 = D1 = D2 = D4
= Open, D3 = GND
–12 –8.5 –5 %
Hysteresis 20 30 mV
Voltage Error Amplifier
Input Bias Current V
CM = 3.0V –0.5 –0.02 0.5 µA
Open Loop Gain 1.5V < V
COMP
< 2.5V, D4 = D3 = D2 = D1 = GND, D0 =
Open
80 dB
Power Supply Rejection Ratio 10.8V < VIN < 15V 85 dB
Output Sourcing Current V
VFB = 2V, VCOMMAND = VCOMP = 2.5V –0.5 –0.3 mA
Output Sinking Current V
VFB = 3V, VCOMMAND = VCOMP = 2.5V 0.5 1 mA
Current Sense Amplifier
Gain 14.25 15.25 V/V
Input Resistance 3kΩ
Common Mode Rejection Ratio 0V < V
CM < 4.5V 60 dB
Power Supply Rejection Ratio 10.8V < VIN < 15V 80 dB
Output Sourcing Current V
IS– = 2V, VISOUT = VIS+ = 2.5V –0.5 –0.3 mA
Output Sinking Current V
IS– = 3V, VISOUT = VIS+ = 2.5V 5 8 mA
Current Amplifier
Input Offset Voltage V
CM = 3.0V –12 12 mV
Input Bias Current V
CM = 3.0V –0.1 µA
Open Loop Gain 1V < V
CAO/ENBL < 2.5V 80 dB
Output Voltage High V
COMP = 3V, VCAM = 2.5V 3.2 V
Power Supply Rejection Ratio 10.8V < VIN < 15V 80 dB
Output Sourcing Current V
CAM = 2V, VCAO/ENBL = VCOMP = 2.5V –1 –0.5 mA
Output Sinking Current V
CAM = 3V, VCAO/ENBL = VCOMP = 2.5V 3 5 mA
Oscillator
Frequency (-4) 85 100 115 kHz
Frequency (-5) 170 200 230 kHz
Frequency (-6) 340 400 460 kHz
Frequency Change With Voltage 10.8V < VIN < 15V 1 %
Output Section
Maximum Duty Cycle 90 95 99 %
Output Low Voltage I
GATE = –100mA 0.2 V
Output High Voltage I
GATE = 100mA 11.8 V
Rise Time C
GATE = 3.3nF 20 70 ns
Fall Time C
GATE = 3.3nF 15 70 ns
Foldback Current Limit
Clamp Level Measured at Voltage EA Output;
V
SENSE = VCOMMAND = 3V
4.28 V
V
COMMAND = 3V, VSENSE = 0 3.64 V
Note 1: This percentage is measured with respect to the ideal COMMAND voltage programmed by the D0 - D4 pins.
Page 4
4
UCC3830-4/-5/-6
CAM (Current Amplifier Inverting Input): The average
load current feedback from ISOUT is applied through a
resistor to this pin. The current loop compensation
network is also connected to this pin (see CAO/ENBL
below).
CAO/ENBL (Current Amplifier Output/Chip Enable):
The current loop compensation network is connected
between this pin and CAM. The voltage on this pin is the
input to the PWM comparator and regulates the output
voltage of the system. The GATE output is disabled
(held low) unless the voltage on this pin exceeds 1V,
allowing the PWM to force zero duty cycle when
necessary. The PWM forces maximum duty cycle when
the voltage on CAO/ENBL exceeds the oscillator peak
voltage (3V). A 3.2V clamp circuit prevents the
CAO/ENBL voltage from rising excessively past the
oscillator peak voltage for excellent transient response.
The user can force this pin below 0.8V externally with an
open collector, disabling the GATE drive.
COMMAND (Digital-to-Analog Converter Output
Voltage): This pin is the output of the 5-bit
digital-to-analog converter (DAC) and the noninverting
input of the voltage amplifier. The voltage on this pin sets
the switching regulator output voltage. This voltage
ranges from 1.8V to 3.5V as programmed by the 5-bit
DAC according to Table 1. The GATE output is disabled
when all 1s or illegal codes are presented at the 5 Bit
DAC. The COMMAND source impedance is typically
1.2kΩ and must therefore drive only high impedance
inputs if accuracy is to be maintained. Bypass
COMMAND with a 0.01µF, low ESR, low ESL capacitor
for best circuit noise immunity.
COMP (Voltage Amplifier Output): The system voltage
compensation network is applied between COMP and
VFB.
D0 - D4 (DAC Digital Input Control Codes): These are
the DAC digital input control codes, with D0 representing
the least significant bit (LSB) and D4, the most significant
bit (MSB) as shown in Table 1. A bit is set low by being
connected to GND. A bit is set high by floating it, or
connecting it to a 5V source. Each control pin is pulled
up to approximately 5V by an internal 70µA current
source.
GATE (PWM Output, MOSFET Driver): This output
provides a 4Ω totem pole driver. Use a series resistor
between this pin and the gate of the external MOSFET to
prevent excessive overshoot.
GND (Signal Ground): All voltages are measured with
respect to GND. Bypass capacitors on the VCC and
VREF pins should be connected directly to the ground
plane near the GND pin.
IS– (Current Sense Amplifier Inverting Input): This pin
is the inverting input to the current sense amplifier and is
connected to the low side of the average current sense
resistor.
IS+ (Current Sense Amplifier Noninverting Input):
This pin is the noninverting input to the current sense
amplifier and is connected to the high side of the
average current sense resistor.
ISOUT (Current Sense Amplifier Output): This pin is
the output of the current sense amplifier. The voltage on
this pin is (COMMAND + G
CSA •I•RSENSE), where
COMMAND is the voltage on the COMMAND pin, G
CSA
is the fixed gain of the current sense amplifier, equal to
15, I is the current through the sense resistor, and
R
SENSE is the value of the average current sensing
resistor.
PGND (Power Ground): This pin provides a dedicated
ground for the output gate driver. The GND and PGND
pins should be connected externally using a short printed
circuit board trace close to the IC. Decouple VIN to
PGND with a low ESR capacitor 0.10µF.
PWRGOOD (Undervoltage/Lower Overvoltage
Output): This pin is an open drain output which is driven
low to reset the microprocessor when VSENSE rises
above or falls below its nominal value by 8.5%. The on
resistance of the open drain switch will be no higher than
470Ω. The OV and UV comparators’ hysteresis is fixed
at 20mV independent of the COMMAND voltage.
VIN (Positive Supply Voltage): This pin supplies power
to the chip. Connect VIN to a stable voltage source of at
least 10.8V. The GATE and PWRGOOD outputs will be
held low until VCC exceeds the upper undervoltage
lockout threshold. This pin should be bypassed directly
to the GND pin.
VFB (Voltage Amplifier Inverting Input): This input is
connected to COMP through a feedback network and to
the power supply output through a resistor or a divider
network.
VREF (Voltage Reference Output): This pin provides
an accurate 5V reference and is internally short circuit
current limited. VREF powers the D/A converter and also
provides a threshold voltage for the UVLO comparator.
For best reference stability, bypass VREF directly to
GND with a low ESR, low ESL capacitor of at least
0.01µF.
PIN DESCRIPTIONS
Page 5
5
UCC3830-4/-5/-6
The curves shown in Figures 1 and 2 depict the typical
high gain-bandwidth products for the UCC3830-x Voltage
Amplifier, Current Amplifier and Current Sense Ampli-
fiers. These high gain-bandwidth devices help achieve
an excellent transient response to load and line changes.
TYPICAL PERFORMANCE CURVES
Figure 1. Open loop gain for UCC3830 voltage and
current amplifier.
Figure 2. Current sense amplifier gain vs frequency.
Short Circuit Current Limit
The short circuit current limit, ISC, is set according to:
ISC =
1.28V
RSENSE • GCSA
where R
SENSE is the average current sense resistor and
GCSA is the current sense amplifier gain. GCSA equals
15.
Example: Choose RSENSE to set the short circuit limit at
17A using the UCC3830-5
RSENSE =
1.28V
17A •15
=0.005Ω
.
A lower resistance value may be needed if the AC ripple
current in the inductor is more than 20% of the load current.
APPLICATION INFORMATION
Figure 3. Short circuit foldback reduces stress on
circuit components by reducing short circuit current.
VSENSE (Output Voltage Sensing Input): This pin is
connected to the system output voltage through a low
pass filter. When the voltage on VSENSE rises above or
falls below the COMMAND voltage by 8.5%, the
PWRGOOD output is driven low to reset the
microprocessor. When the voltage on VSENSE rises
above the COMMAND voltage by 17.5%, the OVP
comparator pulls the current amplifier output voltage
below the oscillator valley voltage to force zero duty
cycle at the GATE output. This pin is also used by the
foldback current limiting circuitry.
PIN DESCRIPTIONS (cont.)
Page 6
6
UCC3830-4/-5/-6
The UCC3830-x incorporates short circuit current
foldback, as shown in Figure 3. When the output of the
power supply is short circuited, the output voltage falls.
When the output voltage reaches 1/2 of its nominal voltage (COMMAND/2) then the output current is reduced.
This feature reduces the amount of current in the
MOSFET, diode and capacitors, and insures high reliability.
Enabling/Disabling the UCC3830-x Gate Drive
The CAO/ENBL pin can be used to disable the UCC3830
gate drive by forcing this pin below 0.8V, as shown in
Figure 4. Bringing the voltage below the valley of the
PWM oscillator ramp will insure a 0% duty cycle, effectively disabling the gate drive. A low noise open collector
signal should be used as an Enable/Disable command.
Setting the Output Voltage Using the DAC
The 5-bit Digital-to-Analog Converter (DAC) is programmed according to Table 1. The COMMAND voltage
is always active as long as the UCC3830 VIN pin is
above the undervoltage lockout voltage. The output gate
drive, GATE, is disabled at certain DAC codes, as shown
in Table 1. Disabling the gate drive disables the power
supply.
Operating the 5-Bit Controller with Intel’s 4-Bit
Pentium Pro
The UCC3830-x 5-Bit Controller is completely backward
compatible. When the fifth bit, D4 is left open (4-Bit Processor in circuit), the UCC3830-x acts as a 4-Bit controller with the COMMAND voltage fully compatible with
Intel’s 4-Bit Pentium
®
Pro family.
APPLICATION INFORMATION (cont.)
Digital Command Command GATEHI/GATELO Digital Command Command GATEHI/GATELO
D4 D3 D2 D1 D0
Voltage Status
D4 D3 D2 D1 D0
Voltage Status
01111 1.300 Note 1 11111 2.000 Note 1
01110 1.350 Note 1 11110 2.100 Enabled
01101 1.400 Note 1 11101 2.200 Enabled
01100 1.450 Note 1 11100 2.300 Enabled
01011 1.500 Note 1 11011 2.400 Enabled
01010 1.550 Note 1 11010 2.500 Enabled
01001 1.600 Note 1 11001 2.600 Enabled
01000 1.650 Note 1 11000 2.700 Enabled
00111 1.700 Note 1 10111 2.800 Enabled
00110 1.750 Note 1 10110 2.900 Enabled
00101 1.800 Enabled 10101 3.000 Enabled
00100 1.850 Enabled 10100 3.100 Enabled
00011 1.900 Enabled 10011 3.200 Enabled
00010 1.950 Enabled 10010 3.300 Enabled
00001 2.000 Enabled 10001 3.400 Enabled
00000 2.050 Enabled 10000 3.500 Enabled
Table 1. Programming the command voltage for the UCC3830-x.
Figure 4. Disabling the UCC3830-x.
Figure 5. Input capacitors current waveform.
UDG-96189
Page 7
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UCC3830-4/-5/-6
Figure 7. Efficiency of UCC3830-5 200kHz demo kit at
2.8V ouput.
Figure 8. UCC3830 configured for 4-bit or 5-bit operation.
UDG-96190-1
Figure 6. Load current vs RMS current for input
capacitors.
APPLICATION INFORMATION (cont.)
Page 8
8
UCC3830-4/-5/-6
Choosing the Input Capacitor
The input capacitors are chosen primarily based on their
switching frequency RMS current handling capability and
their voltage rating. The input capacitors must handle
virtually all of the RMS current at the switching frequency, even if the circuit does not have an input inductor. The switching current in the input capacitors
appears as shown in Figure 5.
The amount of RMS current in an Aluminum Electrolytic
capacitor has a strong impact on the reliability and lifetime of the capacitor. Other factors which affect the life
of an input capacitor are internal heat rise, external airflow, the amount of time that the circuit operates at maximum current and the operating voltage. The curves in
Figure 6 show the RMS current handled by the total input
capacitance in typical VRM circuits delivering 1.8V to
2.8V and powered from 5V.
Related Publications
U-156 and U-157 are Unitrode Application Notes describing the operation of the UC3886 and the UC3886/
UC3910 together in a Pentium® Pro application.
Typical Application
The UCC3830-x is ideal for converting the 5.0V system
bus into the required Pentium® Pro bus voltage. The
3.3V system bus can also be converted using the
UCC3830-x when the Pentium® Pro requires lower bus
voltages.
APPLICATION INFORMATION (cont.)
Table I. Parts list.
REFERENCE
DESIGNATOR
DESCRIPTION PACKAGE
U1 Unitrode UCC3830DWP-5 DAC/PWM SOIC-20 Wide
C1 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can
C2 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can
C3 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can
C4 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can
C5 Sprague/Vishay 595D475X0016A2B, 4.7µF 16V Tantalum SPRAGUE Size A
C6 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can
C7 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can
C8 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can
C9 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can
C10 Sanyo 6MV1500GX, 1500µF, 6.3V, Aluminum Electrolytic 10x20mm Radial Can
C11 Sprague 593D107X9010D2, 100µF, 6.3V Tantalum EIA Size D SMD
C12 0.10µF Ceramic 1206 SMD
C13 0.01µF Ceramic 0603 SMD
C14 0.01µF Ceramic 0603 SMD
C15 0.01µF Ceramic 0603 SMD
C16 1000pF Ceramic 0603 SMD
C17 0.10µF Ceramic 1206 SMD
C18 33pF NPO Ceramic 0603 SMD
C19 1500pF Ceramic 0603 SMD
C20 82pF NPO Ceramic 0603 SMD
C21 0.10µF Ceramic 1206 SMD
C22 0.10µF Ceramic 1206 SMD
CR1 International Rectifier 32CTQ030 30V, 30A Schottky Diode TO-220AB
L1 Micrometals T50-52B, 10 Turns #16AWG, 4.5µH Toroid
Page 9
9
UCC3830-4/-5/-6
UNITRODE CORPORATION
7 CONTINENTALBLVD. • MERRIMACK, NH 03054
TEL. (603) 424-2410 • FAX (603) 424-3460
REFERENCE
DESIGNATOR
DESCRIPTION PACKAGE
Q1 International Rectifier IRL3103, 30V, 56A TO-220AB
R1 Dale/Vishay WSR-2 0.005Ω 1% SMD Power Package
R2 10Ω, 5%, 1/16 Watt 0603 SMD
R3 8.2kΩ, 5%, 1/16 Watt 0603 SMD
R4 6.81kΩ, 1%, 1/16 Watt 0603 SMD
R5 3.92kΩ, 1%, 1/16 Watt 0603 SMD
R6 261kΩ, 1%, 1/16 Watt 0603 SMD
R7 100kΩ, 1%, 1/16 Watt 0603 SMD
R8 3.92kΩ, 1%, 1/16 Watt 0603 SMD
R9 10.5kΩ, 1%, 1/16 Watt 0603 SMD
Q1-HS AAVID 576802 TO-220 Heat Sink TO-220AB
CR1-HS AAVID 577002 TO-220 Heat Sink TO-220AB
Table I. Parts list. (cont.)
Page 10
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