MAX1700 Maxim, MAX1700 Datasheet - Page 12

• Manufacturer Part Number: MAX1700
• Description: 1-Cell to 3-Cell / High-Power 1A / Low-Noise / Step-Up DC-DC Converters
• Manufacturer: Maxim

between the positive battery terminal and GND (Figure
5). The resistor values are then calculated as follows:
where V
and V
into LBP is less than 20nA, R4 can be a large value
(such as 270kΩ or less) without sacrificing accuracy.
The inputs have a common-mode input range from
0.5V to 1.5V and an input-referred hysteresis of 15mV.
The low-battery comparator can also be used to moni-
tor the output voltage, as shown in Figure 6.
To set the low-battery threshold to a voltage below the
1.25V reference, insert a resistor divider between REF
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
Figure 5. Detecting Battery Voltage Above 1.25V
Figure 6. Using the Low-Battery Comparator to Sense the
Output Voltage (MAX1701)
12
R3
R4
0.7V TO 5.5V
______________________________________________________________________________________
LBN
0.22 F
TH
= V
is the desired input voltage trip threshold
CLK/SEL
ONA
ONB
LBP
LBN
REF
REF
GND
MAX1701
R3 = R4(V
PGND
= 1.25V. Since the input bias current
POUT
LBO
LBN
REF
FB
POUT
MAX1701
OUT
POK
LBO
AIN
AO
LX
GND
TH
VOLTAGE MONITOR
LOW-BATTERY MONITOR
ARBITRARY VOLTAGE MONITOR
/V
10
L1
OUT
LBP
0.22 F
LBN
D1
-1)
R3
R4
ARBITRARY
VOLTAGE
R5
R6
and LBN and connect the battery to the LBP input
through a 10kΩ current-limiting resistor (Figure 7). The
equation for setting the resistors for the low-battery
threshold is then as follows:
where V
5, 6, and 7, LBO goes low for a low-voltage input. The
low-battery comparator can be used to check the out-
put voltage or to control the load directly on P
ing start-up (Figure 8). Use the following equation to set
the resistor values:
where V
and V
Figure 7. Detecting Battery Voltages Below 1.25V (MAX1701)
Figure 8. Using the Low-Battery Comparator for Load Control
During Start-Up
BATTERY
VOLTAGE
OUTPUT
C5
LBP
LBP
OUTTH
is connected to the reference or 1.25V.
10k
P
is the desired voltage threshold. In Figures
270k
R3 = R4(V
is the desired output-voltage trip point
R5 = R6(V
POUT
LBO
LBP
MAX1701
0.22 F
GND
0.22 F
C4
OUTTH
C3
REF
LBN
REF
/V
/V
LBP
LBO
LBP
LBP
REF
OUT
MAX1701
-1)
- 1)
10
GND
R5
R6
POUT
LBN
OUT
0.22 F
dur-
R4
R3