Synchronous Controller. UCC2882-1 Datasheet

UCC2882-1 Datasheet PDF


Part Number

UCC2882-1

Description

Average Current Mode Synchronous Controller

Manufacture

Unitrode

Total Page 14 Pages
Datasheet
Download UCC2882-1 Datasheet


UCC2882-1
UCC2882/-1
UCC3882/-1
Average Current Mode Synchronous Controller With 5-Bit DAC
FEATURES
Combined DAC/Voltage Monitor and PWM
with Synchronous Rectification Functions
5-Bit Digital-to-Analog (DAC) Converter
1% DAC/Reference Combined Accuracy
Compatible with 5V and 12V Systems and
12V-only Systems
Low Offset Current Sense Amplifier
Programmable Oscillator Frequency Practical
to 700kHz
Foldback Current Limiting
Overvoltage and Undervoltage Fault Windows
2Totem Pole Outputs with Programmable
Dead Times to Eliminate Cross-Conduction
Chip Disable Function
BLOCK DIAGRAM
DESCRIPTION
The UCC3882 combines high precision reference and voltage
monitoring circuitry with average current mode PWM synchro-
nous rectification controller circuitry to power high-end micropro-
cessors with a minimum of external components. The UCC3882
converts 5V or 12V to an adjustable output ranging from 1.8VDC
to 2.05VDC in 50mV steps and 2.1VDC to 3.5VDC in 100mV
steps with 1% DC system accuracy.
The DAC output voltage is directly compatible with Intel’s 5-bit
VID code (Table 1) which covers 1.3V to 2.05V in 50mV steps
and 2.1V to 3.5V in 100mV steps. The accuracy of the DAC/ref-
erence combination is better than 1%. Undervoltage lockout cir-
cuitry assures the correct logic states at the outputs during
power up and power down. The overvoltage and undervoltage
comparators monitor the system output voltage and indicate
when it rises above or falls below its designed value by more
than 9%. A second overvoltage comparator digitally forces
GATEHI off and GATELO on when the system output voltage ex-
ceeds its designed value by more than 17.5%.
(continued)
03/99
UDG-97047-1

UCC2882-1
ABSOLUTE MAXIMUM RATINGS
VDRVHI, GATEHI (Note 1) . . . . . . . . . . . . . . . . . –0.3V to 20V
VDRVLO, GATELO. . . . . . . . . . . . . . . . . . . . . . . . –0.3V to 15V
All other pins referenced to GND . . . . . . . . . . . . . –0.3V to 5.3V
VIN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +15V
Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . –55°C to +150°C
Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C
CONNECTION DIAGRAM
DIL-28, SOIC-28 (Top View)
N, DW or PW Packages
VSNS 1
PWRGD 2
Currents are positive into, negative out of the specified terminal.
Consult Packaging Section of Databook for thermal limitations
and considerations of packages.
Note 1: 20V at no load. Derate to 18.5V when used with capaci-
tive loads of greater than 1000pF in series with less than 20 .
N/C 3
CAM 4
CAO 5
ISOUT 6
IS+ 7
IS– 8
VIN 9
VDRVLO 10
GATELO 11
PGND 12
RT 13
CT 14
UCC2882/-1
UCC3882/-1
28 GND
27 D0
26 D1
25 N/C
24 D2
23 D3
22 D4
21 VREF
20 COMMAND
19 VDRVHI
18 GATEHI
17 EN
16 COMP
15 VFB
DESCRIPTION (continued)
For all of the parts, grounding the EN pin disables the
GATEHI and GATELO outputs, shutting down the power
supply. For the 2882 and 3882 only, programming a DAC
output voltage below 1.8V, or programming all of the VID
pins high also disables the GATEHI and GATELO out-
puts. For the “–1" option parts, the GATEHI and GATELO
outputs are switching, and the power supply output volt-
age regulates at the programmed DAC output voltage for
all VID codes.
The voltage and current amplifiers have 2.5MHz
gain-bandwidth product to satisfy high performance sys-
tem requirements. The internal current sense amplifier
permits the use of a low value current sense resistor,
minimizing power loss. The oscillator frequency is exter-
nally programmed with RT and CT. The foldback circuit
reduces the converter short circuit current limit to 50% of
its nominal value when the converter is short-circuited,
minimizing component stress and dissipation during ab-
normal conditions. The gate drivers are low impedance
totem pole output stages capable of driving large exter-
nal MOSFETs. Cross conduction is eliminated internally
by programming the dead time between turn-off and turn
on of the external high side and synchronous MOSFETs.
This device is available in a 28-pin wide body surface
mount package. The UCC2882 is specified for operation
from –25°C to +85°C and the UCC3882 is specified for
operation from 0°C to 70°C.
ELECTRICAL CHARACTERISTICS: Unless otherwise specified, VIN = VDRVHI = VDRVLO = 12V, VSNS = 3.5V, VD0 = VD1
= VD2 = VD3 = VD4 = 0V, RT = 13k, CT = 1.8nF, EN = Open, 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
300 500 700 mV
Supply Current
lIN EN = 0V
7 12 mA
2





@ 2014 :: Datasheetspdf.com ::
Semiconductors datasheet search & download site (Privacy Policy & Contact)