L6591 STMicroelectronics, L6591 Datasheet - Page 24

• 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

Application information
6.2
24/41
Figure 42. Timing diagram showing short-circuit behavior
Operation at no load or very light load
When the PWM control voltage at pin COMP falls below a threshold located at 1.75 V, the IC
is disabled with both the high-side and the low-side MOSFET kept in OFF-state, the
oscillator stopped and the quiescent consumption very much reduced to minimize Vcc
capacitor discharge.
The control voltage now will increase as a result of the feedback reaction to the energy
delivery stop and, as it exceeds 1.82 V, the IC will restart switching. After a while, the control
voltage will go down again in response to the energy burst and stop the IC. In this way the
converter will work in a burst-mode fashion with a nearly constant peak current. A further
load decrease will then cause 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. The timing diagram of
operation, showing the most significant signals.
If it is necessary to decrease the intervention threshold of the burst-mode operation, this can
be done by adding a small DC offset on the current sense pin as shown in
Note: The offset reduces the available dynamics of the current signal; thereby, the value of
the sense resistor must be determined taking this offset into account.
LVG,HVG
Vcc_OK
Vcc
(SS pin clamped below 5 V)
Doc ID 14821 Rev 5
Figure 43
illustrates this kind of
Figure 44.
L6591