MAX1640EEE Maxim Integrated Products, MAX1640EEE Datasheet - Page 10

• Manufacturer Part Number: MAX1640EEE
• Description: Current Mode PWM Controllers Adj-Out Switch Mode Current Source
• Manufacturer: Maxim Integrated Products

Specifications of MAX1640EEE

• Number Of Outputs: 1
• Duty Cycle (max): 100 %
• Output Voltage: 2 V to 24 V
• Mounting Style: SMD/SMT
• Package / Case: QSOP-16
• Switching Frequency: 500 KHz
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Synchronous Pin: No
• Topology: Buck
• Case: ssop
• Dc: 99+

If an N-channel MOSFET synchronous rectifier is not
used, a Schottky rectifier is needed. The MAX1640/
MAX1641’s high switching frequency demands a high-
speed rectifier (Table 2). Schottky diodes such as the
1N5817–1N5822 are recommended. Make sure the
Schottky diode’s average current rating exceeds the
peak current limit and that its breakdown voltage
exceeds the output voltage (V
ture applications, Schottky diodes may be inadequate
due to their high leakage current; high-speed silicon
diodes such as the MUR105 or EC11FS1 can be used
instead. At heavy loads and high temperatures, the
benefits of a Schottky diode’s low forward voltage may
outweigh the disadvantage of high leakage current. If
the application uses an N-channel MOSFET synchro-
nous rectifier, a parallel Schottky diode is usually
unnecessary except with very high charge current (> 3
amps). Best efficiency is achieved with both an
N-channel MOSFET and a Schottky diode.
Adjustable-Output, Switch-Mode
Current Source with Synchronous Rectifier
10
Figure 4. Microcontroller Battery Charger
______________________________________________________________________________________
CH0
CH1
I/0
I/0
OUT
). For high-tempera-
Rectifier Diode
D1
D0
MAX1640
GND
NDRV
PGND
TERM
PDRV
CS+
CS-
Refer to the section Programming the Off-Time to select
the proper inductor value. There is a trade-off between
inductor value, off-time, output current ripple, and
switching frequency.
In applications where a microcontroller is available, the
MAX1640/MAX1641 can be used as a low-cost battery
charger (Figure 4). The controller takes over fast
charge, pulse-trickle charge, charge termination, and
other smart functions. By monitoring the output voltage
at V
D1 high), terminates fast charge and initiates top-off
(set D0 high and D1 low), enters trickle charge (set D0
low and D1 high), or shuts off and terminates current
flow (set D0 and D1 low).
__________Applications Information
R3
R4
OUT
N
, the controller initiates fast charge (set D0 and
All-Purpose Microcontroller Battery
DC IN
P
LOW-SIDE IS SHORTED
R
BATT
SENSE
Charger: NiCd, NiMH
T
Inductor Value