MAX1720EUT+T Maxim Integrated Products, MAX1720EUT+T Datasheet - Page 7

• Manufacturer Part Number: MAX1720EUT+T
• Description: IC VOLT INV SW CAP SOT23-6
• Manufacturer: Maxim Integrated Products
• Type: Switched Capacitor (Charge Pump), Invertingr

Specifications of MAX1720EUT+T

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: -1.5 ~ -5.5 V
• Current - Output: 25mA
• Frequency - Switching: 12kHz
• Voltage - Input: 1.5 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-6
• Power - Output: 696mW
• Function: Inverting
• Output Voltage: - 1.25 V to - 5.5 V
• Output Current: 25 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Increasing the flying capacitor’s value reduces the out-
put resistance. Above a certain point, increasing C1’s
capacitance has a negligible effect because the output
resistance becomes dominated by the internal switch
resistance and capacitor ESR.
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:
Bypass the incoming supply to reduce its AC impedance
and the impact of the MAX1719/MAX1720/MAX1721’s
switching noise. A bypass capacitor with a value equal
to that of C1 is recommended.
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.
Table 2. Capacitor Selection for Minimum Output Resistance or Capacitor Size
Table 1. Low-ESR Capacitor Manufacturers
Surface-Mount
Tantalum
Surface-Mount
Ceramic
MAX1719/MAX1721
V
PRODUCTION
RIPPLE
METHOD
MAX1720
PART
=
2
×
_______________________________________________________________________________________
f
OSC
I
OUT
×
Input Bypass Capacitor (C3)
MANUFACTURER
C2
+
Sprague
125kHz
Matsuo
Matsuo
2
12kHz
Output Capacitor (C2)
f
Flying Capacitor (C1)
AVX
AVX
OSC
×
Voltage Inverter
Voltage Inverters with Shutdown
I
OUT
×
ESR
C2
SOT23, Switched-Capacitor
593D, 595D series
CAPACITORS TO MINIMIZE
OUTPUT RESISTANCE
TPS series
267 series
SERIES
(R
X7R
X7R
O
C1 = C2
= 23Ω, TYP)
Two devices can be cascaded to produce an even
larger negative voltage (Figure 4). The unloaded output
voltage is normally -2 x V
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 dra-
matically. For applications requiring larger negative
voltages, see the MAX865 and MAX868 data sheets.
The maximum load current and startup current of the
n
output current capability of the (n - 1)
proper startup.
Figure 4. Cascading MAX1719s or MAX1720s or MAX1721s
to Increase Output Voltage
th
10µF
C1
1µF
cascaded circuit must not exceed the maximum
SHDN (MAX1719)
SHDN (MAX1720/
MAX1721)
6
3
4
MAX1719
MAX1720
MAX1721
803-946-0690
714-969-2491
603-224-1961
803-946-0690
714-969-2491
5
“1”
PHONE
CAPACITORS TO MINIMIZE SIZE
2
1
C1
IN
+V
, but this is reduced slightly
IN
…
…
C2
(R
Cascading Devices
3
4
6
V
O
OUT
C1 = C2
= 40Ω, TYP)
= -nV
0.33µF
MAX1719
MAX1720
MAX1721
3.3µF
th
“n”
5
803-626-3123
714-960-6492
603-224-1430
803-626-3123
714-960-6492
IN
circuit to ensure
FAX
2
1
V
C2
OUT
7