MAX1697(1999) Ver la hoja de datos (PDF) - Maxim Integrated

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componentes Descripción

Fabricante

MAX1697
(Rev.:1999)

60mA, SOT23 Inverting Charge Pump with Shutdown

Maxim Integrated 

60mA, SOT23 Inverting Charge Pump

with Shutdown

Typical Operating Characteristics (continued)

(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25°C, unless otherwise noted.)

MAX1697T

OUTPUT RIPPLE vs. CAPACITANCE

500

450

400

350

300

250

VIN = +4.75V, VOUT = -4.0V

200

VIN = +3.15V, VOUT = -2.5V

150

VIN = +1.9V, VOUT = -1.5V

100

50

0

0 1 2 3 4 5 6 7 8 9 10

CAPACITANCE (µF)

MAX1697U

OUTPUT RIPPLE vs. CAPACITANCE

500

450

400

350

300

250

200

VIN = +4.75V, VOUT = -4.0V

150

VIN = +3.15V, VOUT = -2.5V

100

VIN = +1.9V, VOUT = -1.5V

50

0

0 1 2 3 4 5 6 7 8 9 10

CAPACITANCE (µF)

Pin Description

PIN

NAME

FUNCTION

1

OUT

Inverting Charge-Pump Output

2

IN

Power-Supply Voltage Input. Input

range is 1.5V to 5.5V.

3

C1-

Negative Terminal of the Flying

Capacitor

4

GND Ground

Shutdown Input. Drive this pin high

5

SHDN

for normal operation; drive it low for

shutdown mode. OUT is actively

pulled to ground during shutdown.

6

C1+

Positive Terminal of the Flying

Capacitor

Detailed Description

The MAX1697 capacitive charge pumps invert the volt-

age applied to their input. For highest performance, use

low equivalent series resistance (ESR) capacitors (e.g.,

ceramic).

During the first half-cycle, switches S2 and S4 open,

switches S1 and S3 close, and capacitor C1 charges to

the voltage at IN (Figure 2). During the second half-

cycle, S1 and S3 open, S2 and S4 close, and C1 is level

shifted downward by VIN volts. This connects C1 in par-

allel with the reservoir capacitor C2. If the voltage across

C1

INPUT

1.5V to 5.5V

C3

ON

OFF

6

2

C1+

IN

3

C1-

1

OUT

MAX1697

RL

5 SHDN

GND

4

TE: (

Figure 1. Typical Application Circuit

NEGATIVE

OUTPUT

-1 · VIN

C2

C2 is smaller than the voltage across C1, charge flows

from C1 to C2 until the voltage across C2 reaches

-VIN. The actual voltage at the output is more positive

than -VIN, since switches S1–S4 have resistance and the

load drains charge from C2.

Efficiency Considerations

The efficiency of the MAX1697 is dominated by its qui-

escent supply current (IQ) at low output current and by

its output impedance (ROUT) at higher output current; it

is given by:

η

≅

IOUT

IOUT + IQ



1−

IOUT ⋅ROUT

VIN





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