LT2940CMS datasheet(15/24 Pages) LINER

15 / 24 page

LT2940

2940f

APPLICATIONS INFORMATION

Figure 7. Supply Resistor Reduces Package Heating by Reducing VCC Voltage

When the LATCH pin voltage exceeds 2.5V, the next high

result from the comparator also enables the comparator

latch. The CMPOUT pin goes open (high), and the CMPOUT

pin sinks current (low) regardless of the changes to the

CMP+ level until the latch is cleared. Latch activation is

level sensitive, not edge sensitive, so if CMP+ > 1.24V

when LATCH is brought above 2.5V, the comparator result

is high, and the latch is set immediately. The LATCH pin

voltage may be taken safely to 80V regardless of the VCC

pin voltage.

The latch is released and the comparator reports a low

when LATCH ≤ 0.5V or when VCC < 2.3V regardless of the

CMP+ pin voltage. In this state, the CMPOUT pin sinks

current (low), while the CMPOUT pin goes open (high).

As with latching, clearing is level-sensitive: comparator

outputs react to the input signal as soon as LATCH ≥ 1.25V

and VCC > 2.7V.

Thermal Considerations

If operating at high supply voltages, do not ignore package

dissipation. At 80V the dissipation could reach 400mW;

more if IMON or PMON current exceeds full-scale. Pack-

age thermal resistance is shown in the Pin Conﬁguration

section. Package dissipation can be reduced by simply

adding a dropping resistor in series with the VCC pin, as

shown in Figure 7. The operating range of the current sense

input pins I+ and I–, which extends to 80V independent

of VCC, make this possible. The voltage ranges of the V+,

V–, PMON and IMON pins are, however, limited by VCC.

Consult Table 1 during design. Operating an open-col-

lector output pin with simultaneously large current and

large voltage bias also contributes to package heating and

must be avoided.

CMP+

PMON

IMON

CMPOUT

LATCH

V–

V+

I–

I+

2940 F07

VCC

140k

LOAD

10.0k

5mA

MAX

0A TO 1.3A

100V MAX

VPMON

13.7k

6.19k

OVP

30V TO 80V

OVERPOWER (OVP) GOES HIGH

WHEN LOAD POWER > 40W

LT2940

GND

R12

3.9k

10% 1/8W

150mΩ

1/2W

36V MAX

R14

20k

SCALE = 10

40W FULL-SCALE

kV =

kI = 150mΩ

LT2940CMS датащи(PDF) 15 Page - Linear Technology

LT2940CMS датащи(HTML) 15 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

датащи скачать

ссылки URL