UCC1581 PWM Datasheet

UCC1581 Datasheet, PDF, Equivalent


Part Number

UCC1581

Description

Micropower Voltage Mode PWM

Manufacture

Unitrode

Total Page 15 Pages
Datasheet
Download UCC1581 Datasheet


UCC1581
Micropower Voltage Mode PWM
FEATURES
Low 85µA Startup Current
BLOCK DIAGRAM
Low 300µA Operating Current
Automatically Disabled
Startup Preregulator
Programmable Minimum Duty
Cycle with Cycle Skipping
Programmable Maximum
Duty Cycle
Output Current 1A Peak
Source and Sink
Programmable Soft Start
Programmable Oscillator
Frequency
External Oscillator
Synchronization Capability
application
INFO
available
UCC1581
UCC2581
UCC3581
Note: Pin Connection shown for 14-pin Package
UDG-95011-1
DESCRIPTION
The UCC3581 voltage mode pulse width modulator is de-
signed to control low power isolated DC - DC converters
in applications such as Subscriber Line Power (ISDN
I.430). Primarily used for single switch forward and
flyback converters, the UCC3581 features BiCMOS cir-
cuitry for low startup and operating current, while main-
taining the ability to drive power MOSFETs at
frequencies up to 100kHz. The UCC3581 oscillator al-
lows the flexibility to program both the frequency and the
maximum duty cycle with two resistors and a capacitor. A
TTL level input is also provided to allow synchronization
to an external frequency source.
The UCC3581 includes programmable soft start circuitry,
overcurrent detection, a 7.5V linear preregulator to con-
trol chip VDD during startup, and an on-board 4.0V logic
supply.
The UCC3581 provides functions to maximize light load
efficiency that are not normally found in PWM controllers.
A linear preregulator driver in conjunction with an exter-
nal depletion mode N-MOSFET provides initial controller
power. Once the bootstrap supply is functional, the
preregulator is shut down to conserve power. During light
load, power is saved by providing a programmable mini-
mum duty cycle clamp. When a duty cycle below the
minimum is called for, the modulator skips cycles to pro-
vide the correct average duty cycle required for output
regulation. This effectively reduces the switching fre-
quency, saving significant gate drive and power stage
losses.
The UCC3581 is available in 14-pin plastic and ceramic
dual-in-line packages and in a 14-pin narrow body small
outline IC package (SOIC). The UCC1581 is specified for
operation from 55°C to +125°C, the UCC2581 is speci-
fied for operation from 40°C to +85°C, and the
UCC3581 is specified for operation from 0°C to +70°C.
MARCH 1999 - REVISED MARCH 2003 - SLUS295B

UCC1581
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (IDD 10mA). . . . . . . . . . . . . . . . . . . . . . . . 15V
Supply Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30mA
VREF Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –10mA
OUT Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 1A
Analog Inputs
EN . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to (VDD + 0.3V)
VC, ISEN, SYNC, DCMIN. . . . . . . . . . –0.3V to (VREF + 0.3V)
Power Dissipation at TD = 25°C
(N, J, Q, L Package) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1W
(D Package) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.65W
Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . –55C to +150°C
Lead Temperature (Soldering, 10 sec.) . . . . . . . . . . . . . +300°C
Unless otherwise specified, all voltages are with respect to
Ground. Currents positive into, negative out of the specified ter-
minal. Consult Packaging Section of Databook for thermal limi-
tations and considerations of packages.
CONNECTION DIAGRAMS
DIL-14, SOIC-14 (Top View)
N or J, D Packages
ORDERING INFORMATION
UCC1581J
UCC2581D
UCC2581N
UCC3581D
UCC3581N
TEMPERATURE RANGE
–55°C to +125°C
–40°C to +85°C
–40°C to +85°C
0°C to +70°C
0°C to +70°C
UCC1581
UCC2581
UCC3581
PACKAGE
CDIP
SOIC
PDIP
SOIC
PDIP
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for VDD = 10V, 0.1µF capacitor
from VDD to GND, 1.0µF capacitor from REF to GND, RT1 = 680k, RT2 = 12k, CT = 750pF and TA = TJ.
PARAMETER
TEST CONDITIONS
MIN TYP MAX UNITS
Reference Section
Output Voltage
I = –0.2mA
3.94 4.0 4.06 V
Load Regulation
–5.0mA < I < –0.2mA
20 45 mV
Undervoltage Lockout Section
Start Threshold
6.7 7.3 7.9
V
Minimum Operating Voltage After Start
6.2 6.8 7.4
V
Hysteresis
0.2 0.5 0.8
V
Linear Preregulator Section
Regulated VDD Voltage
7.0 7.5 8.0
V
Regulated VDD to UVLO Delta
100 230 600 mV
VDD Override Threshold
8.2 V
Oscillator Section
Frequency
25°C
18 19.5 21 kHz
Temperature Stability
(Note 1)
3.0 %
CT Peak Voltage
(Note 1)
2.5 V
CT Valley Voltage
(Note 1)
1.0 V
SYNC VIH
1.9 2.1 2.3
V
SYNC VIL
(Note 1)
1.8 V
PWM SECTION
Maximum Duty Cycle
81 84 87 %
Minimum Duty Cycle
(VC < 1.0V) DCMIN = 0V
0%
(VC > 1.0V at start of cycle) DCMIN = 1.18V
7 10 13 %
Input Bias Current
(DCMIN), (Note 1)
–150 20 150 nA
(VC), (Note 1)
–150 20 150 nA
2


Features Micropower Voltage Mode PWM FEATURES Low 85µA Startup Current BLOCK DIAG RAM • Low 300µA Operating Current • Automatically Disabled Startup Prer egulator • Programmable Minimum Duty Cycle with Cycle Skipping • Program mable Maximum Duty Cycle • Output Cu rrent 1A Peak Source and Sink • Prog rammable Soft Start • Programmable O scillator Frequency • External Oscil lator Synchronization Capability appli cation INFO available UCC1581 UCC2581 UCC3581 Note: Pin Connection shown for 14-pin Package UDG-95011-1 DESCRIPTI ON The UCC3581 voltage mode pulse width modulator is designed to control low p ower isolated DC - DC converters in app lications such as Subscriber Line Power (ISDN I.430). Primarily used for singl e switch forward and flyback converters , the UCC3581 features BiCMOS circuitry for low startup and operating current, while maintaining the ability to drive power MOSFETs at frequencies up to 100 kHz. The UCC3581 oscillator allows the flexibility to program both the frequency an.
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