L6591 STMicroelectronics, L6591 Datasheet - Page 21

• Manufacturer Part Number: L6591
• Description: IC CTRLR PWM PROG CM HV 16SOIC
• Manufacturer: STMicroelectronics

Specifications of L6591

• Output Isolation: Isolated
• Frequency Range: 168 ~ 192kHz
• Voltage - Input: 8.7 ~ 22 V
• Power (watts): 750mW
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Output Voltage: 5 V
• Input Voltage: 25 V
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: SMD/SMT
• Duty Cycle (max): 50 %
• For Use With: 497-8335 - BOARD EVAL FOR L6591
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-8286

L6591
6
Application information
The L6591 is an advanced current-mode PWM controller specific for fixed-frequency, peak-
current-mode-controlled ZVS half-bridge converters. In these converters the switches
(MOSFET’s) are controlled with complementary duty cycle: the high-side MOSFET is driven
ON for a duty cycle D and the low-side MOSFET for a duty cycle 1-D. For a proper operation
the maximum allowed duty cycle must be limited below 50%.
An externally programmable dead-time T
and the turn-on of the other one ensures soft-switching and enables high-frequency
operation with high efficiency and low EMI emissions. See
time programming on page 28
The device is able to operate in different modes
load conditions:
1.
2.
Figure 39. Multi-mode operation
Fixed frequency at heavy load. A relaxation oscillator, externally programmable with a
capacitor and a resistor generates a sawtooth and releases clock pulses during the
falling edges of the sawtooth. In this region the low-side MOSFET is turned off by the
even pulses of the clock signal and the high-side MOSFET is turned on after a delay;
the high-side MOSFET is turned off and, after a delay, the low-side MOSFET is turned
on in response to the control loop.
Burst-mode control with no or very light load. When the load is extremely light or
disconnected, the converter will enter a controlled on/off operation with fixed duty cycle,
where a series of few switching cycles are spaced out by long periods where both
MOSFET’s are in OFF-state. A load decrease will be then translated into a frequency
reduction, which can go down even to few hundred hertz, thus minimizing all
frequency-related losses and making it easier to comply with energy saving
regulations. Being the peak current very low, no issue of audible noise arises.
Doc ID 14821 Rev 5
section for more information on how to program T
D
inserted between the turn-off of one MOSFET
(Figure
39), depending on the converter’s
Section 6.6: Oscillator and dead-
Application information
D
.
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