application
INFO
available
UCC1809-1/-2
UCC2809-1/-2
UCC3809-1/-2
Economy Primary Side Controller
FEATURES
•
User Programmable Soft Start With
Active Low Shutdown
•
User Programmable Maximum Duty
Cycle
•
Accessible 5V Reference
•
Undervoltage Lockout
•
Operation to 1MHz
•
0.4A Source/0.8A Sink FET Driver
•
Low 100µA Startup Current
DESCRIPTION
The UCC3809 family of BCDMOS economy low power integrated circuits
contains all the control and drive circuitry required for off-line and isolated
DC-to-DC fixed frequency current mode switching power supplies with
minimal external parts count. Internally implemented circuits include
undervoltage lockout featuring startup current less than 100µA, a user ac-
cessible voltage reference, logic to ensure latched operation, a PWM com-
parator, and a totem pole output stage to sink or source peak current. The
output stage, suitable for driving N-Channel MOSFETs, is low in the off
state.
Oscillator frequency and maximum duty cycle are programmed with two
resistors and a capacitor. The UCC3809 family also features full cycle soft
start.
The family has UVLO thresholds and hysteresis levels for off-line and
DC-to-DC systems as shown in the table to the left.
PART
TURN ON
TURN OFF
NUMBER THRESHOLD THRESHOLD
UCCX809-1
10V
8V
UCCX809-2
15V
8V
The UCC3809 and the UCC2809 are offered in the 8 pin SOIC (D), PDIP
(N), TSSOP (PW), and MSOP (P) packages. The small TSSOP and
MSOP packages make the device ideal for applications where board
space and height are at a premium.
TYPICAL APPLICATION DIAGRAM
R
S TART
V
IN
FB
1
NOIS E
FILTER
FEEDBACK
SS
S LOP E
COMP
DIS ABLE
2
C
S S
1V
1V
+5V
6µA
–
+
+
–
–
+
–
+
15/8V
10/8V
7
17.5V
C
VDD
5V
REF
REF
8
C
REF
V
OUT
CURRENT
S ENS E
0.5V
VDD
UVLO
RT1
3
RT2
4
C
T
OS C
CLK
P WM
LATCH
R
Q
S
OUT
6
GND
5
–
+
V
REF
UDG-99036
SLUS166B - NOVEMBER 1999 - REVISED NOVEMBER 2004
TI [ TEXAS INSTRUMENTS ]
