LM5035EVAL National Semiconductor, LM5035EVAL Datasheet - Page 22

• Manufacturer Part Number: LM5035EVAL
• Description: BOARD EVALUATION LM5035
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM5035EVAL

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Isolated
• Voltage - Output: 3.3V
• Current - Output: 30A
• Voltage - Input: 36 ~ 75V
• Regulator Topology: Buck
• Frequency - Switching: 400kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM5035
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -

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Once the controller has switched to standby mode, the out-
puts no longer switch but the VCC and REF regulators con-
tinue functioning and supply bias to the external circuitry. VCC
Figure 15 shows an application of the OVP comparator for
Remote Thermal Protection using a thermistor (or multiple
thermistors) which may be located near the main heat
sources of the power supply. The negative temperature co-
efficient (NTC) thermistor is nearly logarithmic, and in this
example a 100kΩ thermistor with the β material constant of
4500 kelvins changes to approximately 2kΩ at 130°C. Setting
R1 to one-third of this resistance (665Ω) establishes 130°C
as the desired trip point (for V
HICCUP MODE CURRENT LIMIT RESTART (RES)
The basic operation of the hiccup mode current limit restart is
described in the functional description. The delay time to
REF
= 5V). In a temperature band
FIGURE 14. Latched Load Over-Voltage Protection
FIGURE 15. Remote Thermal Protection
22
must fall below 6.2V or the UVLO pin must fall below 0.4V to
clear the OVP latch.
from 20°C below to 20°C above the OVP threshold, the volt-
age divider is nearly linear with 25mV per°C sensitivity.
R2 provides temperature hysteresis by raising the OVP com-
parator input by R2 x 23µA. For example, if a 22kΩ resistor is
selected for R2, then the OVP pin voltage will increase by
22kΩ x 23µA = 506mV. The NTC temperature must therefore
fall by 506mV / 25mV per°C = 20°C before the LM5035
switches from the standby mode to the normal mode.
restart is programmed with the selection of the RES pin ca-
pacitor C
RES
as illustrated in Figure 15.
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