Datasheet

UCC25600
SLUS846B –SEPTEMBER 2008– REVISED JULY 2011 www.ti.com
Gate Driver
Half-bridge resonant converter is controlled by the nearly 50% duty cycle variable frequency square wave
voltage. This allows the half bridge to be easily driven by the gate-driver transformer. Compared with a
half-bridge driver device, a gate-driver transformer provides a simple and reliable solution, which:
• Eliminate the need for gate driver power supply
• Enable simplified layout
• Preventing shoot through due to the transformer coupling
• No latch up
The UCC25600 integrates two-gate drivers with 0.4-A source and 0.8-A sink capability to directly drive the gate
driver transformer.
For LLC resonant converter, it is critical for the gate-driver signal to be precisely symmetrical. Otherwise, the
resonant tank operation will be symmetrical. The load current distribution will be unbalanced for the output
rectifiers, which in turn requires over design of the power stages and thermal management.
In UCC25600, the gate-driver output is precisely trimmed to have less than 50 ns mismatch. Although the
gate-driver signal is quite symmetrical, it is still recommended to insert the dc blocking capacitor in the
gate-driver transformer primary side to prevent transformer saturation during fast transients.
VCC
Connect a regulated bias supply to VCC pin. When VCC becomes above 10.5 V the device is enabled and after
all fault conditions are cleared the gate driver starts with soft start. When VCC drops below 9.5 V, the device
enters UVLO protection mode and both gate drivers are actively pulled low. When VCC rises above 20 V the
device enters VCC over-voltage protection mode and the device is disabled with both gate drivers actively pulled
low. VCC over-voltage protection will recover with soft start when VCC voltage returns below 18 V.
Over-Temperature Protection
UCC25600 continuously senses its junction temperature. When its junction temperature rises above 160°C the
device will enter over-temperature protection mode with both gate drivers actively pulled low. When junction
temperature drops below 140°C, gate driver restarts with soft start.
REVISION HISTORY
Changes from Revision A (September 2008) to Revision B Page
• Changed Operating temperature range to match the Electrical specifications. ................................................................... 1
• Changed Typical Application Diagram .................................................................................................................................. 1
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