1 Features
1• Pin-for-Pin Compatible With the UC1846
• 65-ns Typical Delay From Shutdown to Outputs,
and 50-ns Typical Delay From SYNC to Outputs
• Improved Current-Sense Amplifier With Reduced
Noise Sensitivity
• Differential Current Sense with 3-V Common-
Mode Range
• Trimmed-Oscillator Discharge Current for
Accurate Deadband Control
• Accurate 1-V Shutdown Threshold
• High-Current Dual Totem-Pole Outputs (1.5-A
peak)
• TTL Compatible Oscillator SYNC Pin Thresholds
• 4-kV ESD Protection

2 Applications
• DC-DC Converters
• Supports Various Topologies:
– Push-Pull, Forward, Half-Bridge, Full Bridge
• Available in Military Temperature range (-55°C to
125°C)

3 Description
The UC1856 is a high-performance version of the
popular UC1846 series of current-mode controllers, and is intended for both design upgrades and new
applications where speed and accuracy are
important. All input-to-output delays have been
minimized, and the current sense output is slew-rate
limited to reduce noise sensitivity. Fast 1.5-A peak
output stages have been added to allow rapid switching of power FETs.
A low-impedance TTL-compatible sync output has
been implemented with a TRI-STATE function when used as a sync input.
Internal-chip grounding has been improved to minimize internal noise caused when driving large
capacitive loads. This improvement, in conjunction
with the improved differential current-sense amplifier,
results in enhanced noise immunity.
Other features include a trimmed oscillator current
(8%) for accurate frequency and dead-time control; a
1-V 5% shutdown threshold; and 4-kV minimum
electrostatic discharge (ESD) protection on all pins.