MAX1595EUA50 Maxim Integrated Products, MAX1595EUA50 Datasheet - Page 4

• Manufacturer Part Number: MAX1595EUA50
• Description: Charge Pumps Regulated 3.3/5.0V Step-Up/Step-Down
• Manufacturer: Maxim Integrated Products

Specifications of MAX1595EUA50

• Function: Step Up, Step Down
• Output Voltage: 5 V
• Output Current: 125 mA
• Maximum Operating Temperature: + 85 C
• Package / Case: uSOP-8
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT

Regulated 3.3V/5.0V Step-Up/Step-Down
Charge Pump
The MAX1595 charge pump provides either a 3.3V or 5V
regulated output. It delivers a maximum 125mA load cur-
rent. In addition, to boost regulating from a lower supply,
it is also capable of buck regulating from supplies that
exceed the regulated output by a diode drop or more.
Designed specifically for compact applications, a com-
plete regulator circuit requires only three small external
capacitors. An innovative control scheme provides con-
stant frequency operation from medium to heavy loads,
while smoothly transitioning to low-power mode at light
loads to maintain optimum efficiency. In buck mode,
switch S1 (in Figure 1) is switched continuously to IN,
while switch S2 alternates between IN and OUT. An
amount of charge proportional to the difference between
the output voltage and the supply voltage is stored on
C
tion point is reached. Maximum output ripple is propor-
tional to the difference between the supply voltage and
the output voltage, as well as to the ratio of the transfer
capacitor (C
The MAX1595 consists of an error amplifier, a 1.23V
bandgap reference, internal resistive feedback network,
oscillator, high-current MOSFET switches, and shutdown
and control logic. Figure 1 shows an idealized unregulat-
ed charge-pump voltage doubler. The oscillator runs at a
50% duty cycle. During one half of the period, the trans-
fer capacitor (C
the other half, the doubler transfers the sum of C
input voltage to the output filter capacitor (C
4
X
MAX1595
, which gets transferred to the output when the regula-
_______________________________________________________________________________________
µMAX
—
1
2
3
4
5
6
7
8
PIN
X
) to the output capacitor (C
THIN QFN-EP
X)
MAX1595
10, 11
2, 3
5, 6
7, 8
charges to the input voltage. During
12
—
1
4
9
Detailed Description
NAME
PGND
AOUT
SHDN
GND
CXN
OUT
CXP
EP
IN
Analog Power and Sense Input for Error Amplifier/Comparator. Connect to OUT at
output filter capacitor.
Shutdown Input. When SHDN = low, the device turns off; when SHDN = high, the device
activates. In shutdown, OUT is disconnected from IN.
Input Supply. Can range from 1.8V to 5.5V. Bypass to GND with a 1µF capacitor.
Ground
Power Ground
Negative Terminal of the Charge-Pump Transfer Capacitor
Positive Terminal of the Charge-Pump Transfer Capacitor
Output. Bypass to GND with output capacitor filter.
Exposed Pad. Internally connected to GND. Connect to a large ground plane to
maximize thermal performance. Not intended as an electrical connection point (thin
QFN package only).
OUT
).
OUT
). Rather
X
and
Figure 1. Unregulated Voltage Doubler
than doubling the input voltage, the MAX1595 provides a
regulated output voltage of either 3.3V or 5.0V.
Driving SHDN low places the device in shutdown mode.
The device draws 0.1µA of supply current in this mode.
When driven high, the MAX1595 enters a soft-start
mode. Soft-start mode terminates when the output volt-
age regulates, or after 2ms, whichever comes first. In
shutdown, the output disconnects from the input.
The MAX1595 has an undervoltage-lockout that deacti-
vates the devices when the input voltage falls below 1.6V.
Below UVLO, hysteresis holds the device in shutdown until
the input voltage rises 40mV above the lockout threshold.
IN
C
IN
FUNCTION
S1
C
Undervoltage Lockout
X
Pin Description
OSC
S2
Shutdown
C
OUT
OUT