UC1875/6/7/8
UC2875/6/7/8
UC3875/6/7/8
APPLICATIONS INFORMATION (cont.)
Slope/Ramp Pins
The ramp generator may be configured for the following
control methods:
• Voltage Mode
• Voltage Feedforward
• Current Mode
• Current Mode with Slope Compensation
Voltage Mode Operation
The figure below shows a voltage-mode configuration.
With R
SLOPE
tied to a stable voltage source, the wave-
form on C
RAMP
will be a constant-slope ramp, providing
conventional voltage-mode control. If R
SLOPE
is con-
nected to the power supply input voltage, a vari-
able-slope ramp will provide voltage feedforward.
1. Simple voltage mode operation
achieved by placing R
SLOPE
between VIN
and SLOPE.
2. Voltage Feedforward achieved by plac-
ing R
SLOPE
between supply voltage and
SLOPE pin of UC1875.
RAMP
V
R s lope
dV
≈
dT R
S LOPE
•
C
R AMP
UDG-95086
For current-mode control the ramp generator may be disabled by grounding the slope pin and using the ramp pin
as a direct current sense input to the PWM comparator.
CONTACT INFORMATION
If you should have questions or need additional information, please contact Jody Bustamante at (903) 868-6132 or
j-busta@ti.com.
11
TI [ TEXAS INSTRUMENTS ]
