参数资料
型号: L5989DTR
厂商: STMICROELECTRONICS
元件分类: 稳压器
英文描述: 5.06 A SWITCHING REGULATOR, 1000 kHz SWITCHING FREQ-MAX, PDSO16
封装: ROHS COMPLIANT, HTSSOP-16
文件页数: 15/51页
文件大小: 1947K
代理商: L5989DTR
Functional description
L5989D
22/51
Doc ID 15778 Rev 3
5.5.4
Thermal shutdown
When the junction temperature reaches 150 °C the device enters in thermal shutdown. Both
MOSFETs are turned off and the soft-start capacitor is discharged with a current of 22 A.
The device doesn’t restart until the junction temperature goes down to 120 °C.
5.6
Power Good
An internal comparator monitors the FB to drive the PGOOD open collector output.
The voltage reference of the comparator is 85% typ. of the nominal FB voltage (0.6V) and an
hysteresis of 5% typ. is provided to increase the noise immunity of the circuitry.
The PGOOD output is driven in low impedance state as long as the output voltage is lower
than VRISING threshold, otherwise released in high impedance.
In case the output voltage drops below the VFALLING threshold the PGOOD output goes in
low impedance.
In case an external type III compensation network is used (see Chapter 6.4.1), the leading
network across the resistor R8 could introduce a phase shift of the sensed FB voltage
respect to the output voltage during load transitions.
5.7
Minimum on time
The L5989D is based on a voltage mode control loop. The advantage of this technique is the
very short conduction time of the power elements thanks to the proper functioning of the
control loop without a current sense (that is challenging with low conduction times), which
instead is required in current mode regulators. The optimized architecture, the design
solutions and the high performance fabrication technique allow power elements to achieve
extremely short conduction times. This allows very high switching frequency operation even
in very low duty cycle applications. Figure 11 shows how the L5989D can easily manage a
minimum conduction time of 200 ns. Moreover, thanks to the embedded P-MOS used for the
high-side, no bootstrap capacitor is required. This means that the device is able to manage
a duty cycle of 100%.
V
RISING
0.85 V
FB
1
R
8
R
6
-------
+
=
V
FALLING
0.80 V
FB
1
R
8
R
6
-------
+
=
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