LM5008EVAL National Semiconductor, LM5008EVAL Datasheet - Page 8

• Manufacturer Part Number: LM5008EVAL
• Description: EVALUATION BOARD FOR LM5008
• Manufacturer: National Semiconductor

Specifications of LM5008EVAL

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 10V
• Current - Output: 300mA
• Voltage - Input: 12 ~ 95V
• Regulator Topology: Buck
• Board Type: Fully Populated
• Utilized Ic / Part: LM5008
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -
• Frequency - Switching: -
• Other names: *LM5008EVAL

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High Voltage Start-Up Regulator
The LM5008 contains an internal high voltage startup regu-
lator. The input pin (V
voltages up to 95 Volts, with transient capability to 100 volts.
The regulator is internally current limited to 9.5mA at V
Upon power up, the regulator sources current into the external
capacitor at V
es the under-voltage lockout threshold of 6.3V, the buck
switch is enabled.
Regulation Comparator
The feedback voltage at FB is compared to an internal 2.5V
reference. In normal operation (the output voltage is regulat-
ed), an on-time period is initiated when the voltage at FB falls
below 2.5V. The buck switch will stay on for the on-time,
causing the FB voltage to rise above 2.5V. After the on-time
period, the buck switch will stay off until the FB voltage again
falls below 2.5V. During start-up, the FB voltage will be below
2.5V at the end of each on-time, resulting in the minimum off-
time of 300 ns. Bias current at the FB pin is nominally 100 nA.
CC
(C3). When the voltage on the V
IN
) can be connected directly to the line
FIGURE 9. Low Ripple Output Configuration
FIGURE 10. Self Biased Configuration
CC
pin reach-
CC
.
8
In applications involving a high value for V
dissipation in the V
age can be diode connected to the V
auxiliary voltage to 8.0 -14V will shut off the internal regulator,
reducing internal power dissipation. See Figure 10. The cur-
rent required into the V
Over-Voltage Comparator
The feedback voltage at FB is compared to an internal 2.875V
reference. If the voltage at FB rises above 2.875V the on-time
pulse is immediately terminated. This condition can occur if
the input voltage, or the output load, change suddenly. The
buck switch will not turn on again until the voltage at FB falls
below 2.5V.
CC
regulator is a concern, an auxiliary volt-
CC
pin is shown in Figure 2.
20097905
20097906
CC
IN
pin. Setting the
, where power