MAX1637EEE Maxim Integrated Products, MAX1637EEE Datasheet - Page 14

• Manufacturer Part Number: MAX1637EEE
• Description: IC CTRLR MINI LV STPDWN 16-QSOP
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX1637EEE

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.1 ~ 5.5 V
• Current - Output: 3A
• Frequency - Switching: Adj to 350kHz
• Voltage - Input: 3.15 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Power - Output: 667mW
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Miniature, Low-Voltage,
Precision Step-Down Controller
make prototype troubleshooting difficult since only
20ms or 30ms elapse before the SMPS is latched off.
The overvoltage crowbar protection is disabled in out-
put undervoltage mode.
The overvoltage crowbar-protection circuit is intended
to blow a fuse in series with the battery if the main
SMPS output rises significantly higher than its standard
level (Table 4). In normal operation, the output is com-
pared to the internal precision reference voltage. If the
output goes 7% above nominal, the synchronous-recti-
fier MOSFET turns on 100% (the high-side MOSFET is
simultaneously forced off) in order to draw massive
amounts of battery current to blow the fuse. This safety
feature does not protect the system against a failure of
the controller IC itself, but is intended primarily to guard
against a short across the high-side MOSFET. A crow-
bar event is latched and can only be reset by a rising
edge on SHDN (or by removal of the V
age). The overvoltage-detection decision is made rela-
tive to the regulation point.
Soft-start allows a gradual increase of the internal cur-
rent-limit level at start-up to reduce input surge cur-
rents. The SMPS contains an internal digital soft-start
circuit controlled by a counter, a digital-to-analog con-
verter (DAC), and a current-limit comparator. In shut-
down, the soft-start counter is reset to zero. When the
SMPS is enabled, its counter starts counting oscillator
pulses, and the DAC begins incrementing the compari-
son voltage applied to the current-limit comparator. The
DAC output increases from 0mV to 100mV in five equal
steps as the count increases to 512 clocks. As a result,
the main output capacitor charges up relatively slowly.
Table 4. Operating Modes
14
Undervoltage
Overvoltage
______________________________________________________________________________________
(Crowbar)
Shutdown
Lockout
Output
MODE
Run
Internal Digital Soft-Start Circuit
Output Overvoltage Protection
SHDN
High
High
High
Low
V
V
above regulation point
V
nominal after 20ms to
30ms timeout expires
OUT
OUT
OUT
CC
CONDITIONS
in regulation
greater than 7%
below 70% of
supply volt-
—
The exact time of the output rise depends on output
capacitance and load current, but it is typically 1ms
with a 300kHz oscillator.
The output voltage is set via a resistor divider connect-
ed to FB (Figure 1). Calculate the output voltage with
the following formula:
where V
Recommended normal values for R3 range from 5kΩ to
100kΩ. To achieve a 1.1V nominal output, connect FB
directly to CSL. Remote output voltage sensing is pos-
sible by using the top of the external resistor divider as
the remote sense point.
The standard application circuit (Figure 1) contains a
ready-to-use solution for common application needs.
Use the following design procedure to optimize the
basic schematic for different voltage or current require-
ments. But before beginning a design, firmly establish
the following:
• Maximum input (battery) voltage, V
• Minimum input (battery) voltage, V
__________________Design Procedure
All circuit blocks active
All circuit blocks off
REF = off, DL = high
REF = off, DL = low
value should include the worst-case conditions, such
as no-load operation when a battery charger or AC
adapter is connected but no battery is installed.
V
should be taken at full load under the lowest battery
conditions. If the minimum input-output difference is
less than 1.5V, the filter capacitance required to
maintain good AC load regulation increases (see
Low-Voltage Operation section).
IN(MAX)
STATUS
REF
must not exceed 30V.
= 1.1V nominal.
V
OUT
= V
Setting the Output Voltage
REF
Normal operation
Lowest current consumption
Rising edge on SHDN exits
crowbar
Rising edge on SHDN exits
UVLO
(1 + R2 / R3)
NOTES
IN(MIN)
IN(MAX)
. This value
. This