MAX1705EEE+T Maxim Integrated Products, MAX1705EEE+T Datasheet - Page 14

• Manufacturer Part Number: MAX1705EEE+T
• Description: IC DC-DC CONV LN 16-QSOP
• Manufacturer: Maxim Integrated Products
• Type: Step-Up (Boost)r

Specifications of MAX1705EEE+T

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 2.5 ~ 5.5 V
• Current - Output: 850mA
• Frequency - Switching: 300kHz
• Voltage - Input: 0.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Power - Output: 696mW
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LBP is less than 50nA, R6 can be a large value (such
as 270kΩ or less) without sacrificing accuracy.
Connect the resistor voltage-divider as close to the IC
as possible, within 0.2in. (5mm) of the LBP pin. The
inputs have a 0.5V to 1.5V common-mode input range,
and a 16mV input-referred hysteresis.
The low-battery comparator can also be used to moni-
tor the output voltage, as shown in Figure 5.
To set the low-battery threshold to a voltage below the
1.25V reference, insert a resistor-divider between REF
and LBN, and connect the battery to the LBP input
through a 10kΩ current-limiting resistor (Figure 6). The
equation for setting the resistors for the low-battery
threshold is then as follows:
Alternatively, the low-battery comparator can be used
to check the output voltage or to control the load direct-
ly on POUT during startup (Figure 7). Use the following
equation to set the resistor values:
where V
and V
The MAX1705/MAX1706 have an internal 1.250V, 1%
bandgap reference. Connect a 0.33µF bypass capaci-
tor to GND within 0.2in. (5mm) of the REF pin. REF can
source up to 50µA of external load current.
Set the step-up converter output voltage between 2.5V
and 5.5V by connecting a resistor voltage-divider to FB
from OUT to GND, as shown in Figure 8. The resistor
values are then as follows:
where V
1.233V. Since the input bias current into FB is less than
50nA, R2 can have a large value (such as 270kΩ or
1- to 3-Cell, High-Current, Low-Noise,
Step-Up DC-DC Converters with Linear Regulator
14
_________________ Design Procedure
______________________________________________________________________________________
LBP
OUT,TH
FB
is connected to the reference or 1.25V.
, the step-up regulator feedback setpoint, is
is the desired output voltage trip point
R
R
R
5
1
5
Setting the Output Voltages
=
=
=
R
R
R
2
6
6
⎛
⎜
⎝
⎛
⎜
⎝
⎛
⎜
⎝
V
V
V
V
POUT
IN TH
V
OUT TH
REF
V
FB
,
LBP
,
- 1
- 1
- 1
⎞
⎟
⎠
⎞
⎟
⎠
⎞
⎟
⎠
Reference
Figure 5. Using the Low-Battery Comparator to Sense
the Output Voltage
Figure 6. Detecting Battery Voltages Below 1.25V
Figure 7. Using the Low-Battery Comparator for Load Control
During Startup
C5
BATTERY
VOLTAGE
0.33µF
P
10kΩ
R8
270kΩ
POUT
LBO
LBP
POUT
LBO
LBN
REF
MAX1705
MAX1706
MAX1705
MAX1706
0.33µF
STEP-UP OUTPUT
C4
0.1µF
GND
GND
C3
REF
LBN
LDO
LBP
LBO
LBP
REF
OUT
MAX1705
MAX1706
GND
POUT
R5
R6
R5
R6
LBN
0.33µF
R6
R5