AN2208 datasheet(48/51 Pages) STMICROELECTRONICS

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7 Test results

AN2208

48/51

C.3

L5970D DC/DC converter load test results

The DC/DC converter was tested with a constant output current with resistive load.

The Waveform on coil L1 has to be clear without overshot (see Figure 61., Figure 63.).

Input/output voltage ripple depends on ESR capacitor values.

Only low ESR capacitors have been used on VSS and VOUT.

Test conditions

●

Resistive load = 12

Ω.

●

Input voltages VSS = 8, 12, and 24V.

●

Output voltage VBSS = 5V

●

Output current IOUTDC = 0.4A

●

Ambient Temperature (TA) = 25°C

Test results: If output current is increase up to 1.4 A, then the current limiter will be active.

Output voltage ripple can be seen in Figure 62. The maximum value of ripple is 93 mV. The

efficiency measurement results are shown in Figure 58.

Table 14.

L5970D electrical characteristics

Symbol

Parameter

Min.

Typ.

Max.

Unit

VSS

Operating input voltage

6.6

IQOP

Total operating quiescent current

2.4

IOUTDC

Maximum limiting current

1.0

1.4

Switching frequency

243

250

kHz

Duty cycle

100

Operating Temperature Range

–25 to 85°C

°C

PTOTDC

Power dissipation at Tamb = 60°C

0.75

Figure 58. Efficiency vs. output current

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