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2
UC1874-1,-2
UC2874-1,-2
UC3874-1,-2
DIL-18 (TOP VIEW)
J or N, DW Packages
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36V
Boost Voltage (BOOT). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50V
OUTPUT Drivers (HDRIVE, LDRIVE) Currents
(continuous) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±0.25A
(peak) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±1A
VREF Current . . . . . . . . . . . . . . . . . . . . . . . . Internally Limited
Inputs (VSNS, SS, COMP, CT). . . . . . . . . . . . . . . . -0.3 to 10V
Inputs (ISNS+, ISNS-) . . . . . . . . . . . . . . . . . . . . . . . -0.3 to 20V
Outputs (CAOUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to10V
Soft start Sinking Current . . . . . . . . . . . . . . . . . . . . . . . . 1.5mA
Storage Temperature . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Junction Temperature. . . . . . . . . . . . . . . . . . . –65°C to +150°C
Lead Temperature (Soldering, 10 sec.). . . . . . . . . . . . . +300°C
All currents are positive into, negative out of the specified ter-
minal. All voltages are referenced to GND. Consult Packaging
Section of Databook for thermal limitations and considerations
of packages.
CONNECTION DIAGRAMS
During standby operation, the output capacitor supplies
all of the load current requirements. Normal operation re-
turns when the output voltage has drooped by 1%. Re-
verse current in the inductor is prevented by on-chip
circuitry providing additional efficiency improvements.
Virtual 100% duty cycle operation is easily attained by
the controller even though a bootstrapped high side drive
technique is employed.
A low power sleep mode can be invoked through the SS
pin. Quiescent supply current in sleep mode is typically
less than 50mA. Two UVLO options are available. The
UC3874-1 is designed for logic level MOSFETs and has
UVLO turn-on and turn-off thresholds of 4.5V and 4.4V
respectively. The UC3874-2 is designed for standard
power MOSFETs and has UVLO turn-on and turn-off
thresholds of 10V and 9V respectively. A precision 2.5V
reference can supply 20mA to external circuitry. An error
amplifier with soft start, high bandwidth current amplifier,
and a synchronizable oscillator are additional features.
Available packages include 18-pin plastic and ceramic
DIP (N, J), 18-pin SOIC (DW), and 20-pin plastic and
ceramic leadless chip carriers (Q, L).
PLCC-20 (TOP VIEW)
Q Package
LCC-28 (TOP VIEW)
L Package