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MAX1853EXTMAXN/a2avaiSC70 Inverting Charge Pumps with Shutdown


MAX1853EXT ,SC70 Inverting Charge Pumps with ShutdownApplicationsNegative Supply from +5V or +3.3V Logic SuppliesSmall LCD PanelsOrdering InformationGaA ..
MAX1853EXT-T ,SC70 Inverting Charge Pumps with ShutdownApplicationsNegative Supply from +5V or +3.3V Logic SuppliesSmall LCD PanelsOrdering InformationGaA ..
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MAX1856EUB+ ,Wide-Input-Range, Synchronizable, PWM SLIC Power SupplyELECTRICAL CHARACTERISTICS(V = SYNC/SHDN, V = 5V, V = 5V, R = 200kΩ, T = 0°C to +85°C. Typical valu ..
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MAX4762EUB+ ,Low-Voltage, Dual SPDT, Audio Clickless Switches with Negative Rail CapabilityELECTRICAL CHARACTERISTICS(V = +2.7V to +5.5V, T = -40°C to +85°C, unless otherwise noted. Typical ..
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MAX1853EXT
SC70 Inverting Charge Pumps with Shutdown
General Description
The MAX1852/MAX1853 monolithic, CMOS charge-
pump voltage inverters in the ultra-small SC70 package
feature a low 15Ωoutput resistance, permitting loads
up to 30mA with maximum efficiency. The MAX1852/
MAX1853 are available with operating frequencies of
50kHz and 200kHz, respectively, allowing optimization
of supply current or external component size. Small
external components and micropower shutdown mode
make these devices ideal for both battery-powered and
board-level voltage conversion applications.
Oscillator control circuitry and four power-MOSFET
switches are included on-chip. Applications include
generating a negative supply from a +5V or +3.3V logic
supply to power analog circuitry. Both versions come in
a 6-pin SC70 package that is 40% smaller than a
SOT23.
Applications

Negative Supply from +5V or +3.3V Logic Supplies
Small LCD Panels
GaAsFET Bias Supplies
Handy-Terminals, PDAs
Battery-Operated Equipment
Features
30mA Output Current Low 15ΩOutput Resistance68µA Supply Current (MAX1852)Requires Only Two 0.68µF Capacitors (MAX1853)+2.5V to +5.5V Input Voltage Range0.1µA Logic-Controlled ShutdownTwo Switching Frequencies
50kHz (MAX1852)
200kHz (MAX1853)
Slew-Rate Limited to Reduce EMIUltra-Small 6-Pin SC70 Package
MAX1852/MAX1853
SC70 Inverting Charge Pumps
with Shutdown
Pin Configurationypical Operating Circuit

19-1792; Rev 0; 9/00
MAX1852/MAX1853
SC70 Inverting Charge Pumps
with Shutdown
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, capacitors from Table 2, VIN= +5V, SHDN= IN, TA= -40°C to +85°C, unless otherwise noted. Typical values are
at TA= +25°C.) (Note 1)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN to GND.................................................................-0.3V to +6V
C1+, SHDNto GND.....................................-0.3V to (VIN + 0.3V)
C1- to GND...............................................(VOUT- 0.3V) to +0.3V
OUT to GND.............................................................+0.3V to -6V
OUT Short-Circuit to GND..............................................1 minute
Continuous Power Dissipation (TA= +70°C)
6-Pin SC70 (derate 3.1mW/°C above +70°C) .............245mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Note 2:
Output resistance is guaranteed with capacitor ESR of 0.3Ωor less.
MAX1852/MAX1853
SC70 Inverting Charge Pumps
with Shutdown

MAX1853
OUTPUT RESISTANCE vs. TEMPERATURE
MAX1852/3 toc09
TEMPERATURE (°C)
OUTPUT RESISTANCE (
MAX1852
OUTPUT RESISTANCE vs. TEMPERATURE
MAX1852/3 toc08
TEMPERATURE (°C)
OUTPUT RESISTANCE (
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX1852/3 toc07
SUPPLY CURRENT (nA)
MAX1852
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1852/3 toc01
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
MAX1853
EFFICIENCY vs. LOAD CURRENT
MAX1852/3 toc04
LOAD CURRENT (mA)
EFFICIENCY (%)
MAX1853
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX1852/3 toc02
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
MAX1852
EFFICIENCY vs. LOAD CURRENT
MAX1852/3 toc03
LOAD CURRENT (mA)
EFFICIENCY (%)
OUTPUT RESISTANCE vs. INPUT VOLTAGE
MAX1852/3 toc05
INPUT VOLTAGE (V)
OUTPUT RESISTANCE (
NO-LOAD SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX1852/3 toc06
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
Typical Operating Characteristics

(Circuit of Figure 1, capacitors from Table 2, VIN= +5V, SHDN= IN, TA= +25°C, unless otherwise noted.)
MAX1852/MAX1853
SC70 Inverting Charge Pumps
with Shutdownypical Operating Characteristics (continued)

(Circuit of Figure 1, capacitors from Table 2, VIN= +5V, SHDN= IN, TA= +25°C, unless otherwise noted.)
Detailed Description
The MAX1852/MAX1853 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 VINvolts. This connects C1 in par-
allel with the reservoir capacitor C2. If the voltage across
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 -VINsince switches S1–S4 have resistance and the
load drains charge from C2.
Efficiency Considerations

The efficiency of the MAX1852/MAX1853is dominated
by their quiescent supply current (IQ) at low output cur-
rent and by their output impedance (ROUT) at higher
output current; it is given by:
where the output impedance is roughly approximated
by:
The first term is the effective resistance of an ideal
switched-capacitor circuit (Figures 3a and 3b), and
RSWis the sum of the charge pump’s internal switch
resistances (typically 6Ωat VIN= +5V). The typical out-
put impedance is more accurately determined from the
Typical Operating Characteristics.
Shutdown

The MAX1852/MAX1853have a logic-controlled shut-
down input. Driving SHDNlow places the devices in a
low-power shutdown mode. The charge-pump switch-
ing halts, supply current is reduced to 2nA.
Driving SHDNhigh will restart the charge pump. The
switching frequency and capacitor values determine how
soon the device will reach 90% of the input voltage.
Applications Information
Capacitor Selection

The charge-pump output resistance is a function of the
ESR of C1 and C2. To maintain the lowest output resis-
tance, use capacitors with low ESR. (See Table 1 for a
list of recommended manufacturers.) Tables 2 and 3
suggest capacitor values for minimizing output resis-
tance or capacitor size.
Flying Capacitor (C1)

Increasing the flying capacitor’s value reduces the out-
put resistance. Above a certain point, increasing C1’s
capacitance has negligible effect because the output
resistance is then dominated by internal switch resis-
tance and capacitor ESR.
Output Capacitor (C2)

Increasing the output capacitor’s value reduces the
output ripple voltage. Decreasing its ESR reduces both
output resistance and ripple. Lower capacitance values
can be used with light loads if higher output ripple can
be tolerated. Use the following equation to calculate the
peak-to-peak ripple:
MAX1852/MAX1853
SC70 Inverting Charge Pumps
with Shutdown
Pin Description
TE: (
MAX1852/MAX1853
SC70 Inverting Charge Pumps
with Shutdown
Input Bypass Capacitor (C3)

If necessary, bypass the incoming supply to reduce its
AC impedance and the impact of the MAX1852/
MAX1853s’ switching noise. A bypass capacitor with a
value equal to that of C1 is recommended.
Voltage Inverter

The most common application for these devices is a
charge-pump voltage inverter (Figure 1). This applica-
tion requires only two external components—capacitors
C1 and C2—plus a bypass capacitor, if necessary.
Refer to the Capacitor Selection section for suggested
capacitor types.
Cascading Devices

Two devices can be cascaded to produce an even
larger negative voltage (Figure 4). The unloaded output
voltage is normally -2 ✕VIN, but this is reduced slightly
by the output resistance of the first device multiplied by
the quiescent current of the second. When cascading
more than two devices, the output resistance rises sig-
nificantly. For applications requiring larger negative
voltages, see the MAX865 and MAX868 data sheets.
Paralleling Devices

Paralleling multiple MAX1852/MAX1853s reduces the
output resistance. Each device requires its own pump
capacitor (C1), but the reservoir capacitor (C2) serves
all devices (Figure 5). Increase C2’s value by a factor of
n, where nis the number of parallel devices. Figure 5
shows the equation for calculating output resistance.
Combined Doubler/Inverter

In the circuit of Figure 6, capacitors C1 and C2 form the
inverter, while C3 and C4 form the doubler. C1 and C3
are the pump capacitors; C2 and C4 are the reservoir
capacitors. Because both the inverter and doubler use
part of the charge-pump circuit, loading either output
causes both outputs to decline toward GND. Make sure
the sum of the currents drawn from the two outputs
does not exceed 30mA.
Heavy Load Connected to a
Positive Supply

Under heavy loads, where a higher supply is sourcing
current into OUT, the OUT supply must not be pulled
above ground. Applications that sink heavy current into
OUT require a Schottky diode (1N5817) between GND
and OUT, with the anode connected to OUT (Figure 7).
Layout and Grounding

Good layout is important, primarily for good noise per-
formance. To ensure good layout, mount all compo-
nents as close together as possible, keep traces short
to minimize parasitic inductance and capacitance, and
use a ground plane.
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