MAX630EJA MAXIM [Maxim Integrated Products], MAX630EJA Datasheet - Page 5

• Manufacturer Part Number: MAX630EJA
• Description: CMOS Micropower Step-Up Switching Regulator
• Manufacturer: MAXIM [Maxim Integrated Products]

The low-battery detector compares the voltage on LBR
with the internal 1.31V reference. The output, LBD, is an
open-drain N-channel MOSFET. In addition to detecting
and warning of a low battery voltage, the comparator
can also perform other voltage-monitoring operations
such as power-failure detection.
Another use of the low-battery detector is to lower the
oscillator frequency when the input voltage goes below
a specified level. Lowering the oscillator frequency
increases the available output power, compensating for
the decrease in available power caused by reduced
input voltage (see Figure 5).
The shutdown mode is entered whenever I
driven below 0.2V or left floating. When shut down, the
Figure 1. +5V to +15V Converter and Block Diagram
+5V INPUT
D1
1N4148
L1
470
LOW BATTERY INPUT
169kΩ
R3
_______________________________________________________________________________________
Logic-Level Shutdown Input
R4
100kΩ
1 LBR
2 C
3 L
4 GND
R
X
X
ON
Low-Battery Detector
≅ 3Ω
40kHz
OSC
1.31V
C
(pin 6) is
COMP 2
COMP 2
CMOS Micropower Step-Up
MAX630
MAX630’s analog circuitry, oscillator, L
puts are turned off. The device’s quiescent current dur-
ing shutdown is typically 10nA (1µA max).
In most circuits, the preferred source of +V
the MAX630 and MAX4193 is the boosted output volt-
age. This is often referred to as a “bootstrapped” oper-
ation since the circuit figuratively “lifts” itself up.
The on-resistance of the N-channel L
es with an increase in +V
ing current goes up with +V
Operating Characteristics, I
with very low output current and input voltages greater
than 3V, it may be more efficient to connect +V
ly to the input voltage rather than bootstrap.
BIAS GENERATOR
COMP 1
REFERENCE
BANDGAP
1.31V
AND
Switching Regulator
LBD 8
+V
V
FB
I
C
S
7
6
5
C
Bootstrapped Operation
C
S
; however, the device operat-
S
vs. +V
R1
499kΩ
S
C1
470μF
25V
LOW-BATTERY OUTPUT
(LOW IF INPUT < 3V)
47.5kΩ
S
(see the Typical
R2
X
graph). In circuits
SHUTDOWN
X
output decreas-
, and LBD out-
OPERATE
+15V OUTPUT
20mA
S
voltage for
S
direct-
5