LM2651MTC-1.8 National Semiconductor, LM2651MTC-1.8 Datasheet - Page 7

• Manufacturer Part Number: LM2651MTC-1.8
• Description: 1.5A High Efficiency Synchronous Switching Regulator
• Manufacturer: National Semiconductor

Typical Performance Characteristics
Current Limit vs Junction
Temperature (V
Block Diagram
Operation
The LM2651 operates in a constant frequency (300 kHz),
current-mode PWM for moderate to heavy loads; and it auto-
matically switches to hysteretic mode for light loads. In hys-
teretic mode, the switching frequency is reduced to keep the
efficiency high.
OUT
= 3.3V)
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Current Limit vs Input
Voltage (V
FIGURE 1. LM2651 Block Diagram
OUT
= 3.3V)
(Continued)
7
Main Operation
When the load current is higher than the sleep mode thresh-
old, the part is always operating in PWM mode. At the begin-
ning of each switching cycle, the high-side switch is turned
on, the current from the high-side switch is sensed and com-
pared with the output of the error amplifier (COMP pin).
When the sensed current reaches the COMP pin voltage
level, the high-side switch is turned off; after 40 ns (dead-
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