MAX1830EEE+ Maxim Integrated Products, MAX1830EEE+ Datasheet - Page 8

• Manufacturer Part Number: MAX1830EEE+
• Description: IC REG STEP DOWN 3A 16-QSOP
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX1830EEE+

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.5V, 1.8V, 2.5V, Adj
• Current - Output: 3A
• Frequency - Switching: 1MHz
• Voltage - Input: 3 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Power - Output: 1.12W
• Output Voltage: 1.5 V to 2.5 V
• Output Current: 3.4 A
• Input Voltage: 3 V to 5.5 V
• Supply Current: 750 uA
• Switching Frequency: 1 MHz
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

device operates in discontinuous conduction. Current-
sense circuitry monitors the current through the NMOS
synchronous switch, turning it off before the current
reverses. This prevents current from being pulled from
the output filter through the inductor and NMOS switch to
ground. As the device switches between operating
modes, no major shift in circuit behavior occurs.
When the input voltage drops near the output voltage,
the duty cycle increases until the PMOS MOSFET is on
continuously. The dropout voltage in 100% duty cycle
is the output current multiplied by the on-resistance of
the internal PMOS switch and parasitic resistance in the
inductor. The PMOS switch remains on continuously as
long as the current limit is not reached.
Soft-start allows a gradual increase of the current-limit
level at startup to reduce input-surge currents. The
MAX1830/MAX1831 contain internal digital soft-start cir-
cuits, controlled by a counter, a digital-to-analog con-
verter (DAC), and the current-limit comparator. At
power-on or in shutdown mode, the soft-start counter is
reset to zero. When the MAX1830/MAX1831 are enabled
or powered up, its counter starts counting LX switching
cycles, and the DAC begins incrementing the compari-
son voltage applied to the current-limit comparator. The
DAC ramps up the internal current limit in four 25%
steps, as the count increases to 256 cycles. As a result,
the main output capacitor charges up relatively slowly.
The exact time of the output rise depends on nominal
switching frequency, output capacitance, and the load
current, and is typically 1ms.
Drive SHDN to a logic-level low to place the
MAX1830/MAX1831 in low-power shutdown mode and
3A, 1MHz, Low-Voltage, Step-Down Regulators with
Synchronous Rectification and Internal Switches
Table 1. Recommended Component Values (I
8
_______________________________________________________________________________________
V
IN
3.3
3.3
3.3
3.3
5
5
5
5
5
(V)
Internal Digital Soft-Start Circuit
100% Duty-Cycle Operation
V
OUT
3.3
2.5
1.8
1.5
1.1
2.5
1.8
1.5
1.1
(V)
Shutdown
f
PWM
800
865
850
860
625
570
850
860
680
(kHz)
OUT
reduce supply current to less than 1µA. In shutdown, all
circuitry and internal MOSFETs turn off, and the LX
node becomes high impedance. Drive SHDN to a
logic-level high or connect to V
Three signals are added together at the input of the
summing comparator (Figure 2): an output-voltage error
signal relative to the reference voltage, an integrated
output-voltage error correction signal, and the sensed
PMOS switch current. The integrated error signal is pro-
vided by a transconductance amplifier with an external
capacitor at COMP. This integrator provides high DC
accuracy without the need for a high-gain amplifier.
Connecting a capacitor at COMP modifies the overall
loop response (see Integrator Amplifier).
Figure 3. Maximum Recommended Operating Frequency vs.
Input Voltage
= 3.0A)
1400
1200
1000
800
600
400
200
0
OPERATING FREQUENCY vs. INPUT VOLTAGE
2.6
L (µH)
V
2.2
2.2
2.2
2.2
2.2
1.5
1.5
1.5
1.5
OUT
V
OUT
3.1
MAXIMUM RECOMMENDED
= 1.5V
= 1.8V
3.6
V
OUT
V
= 2.5V
Summing Comparator
IN
4.1
(V)
CC
V
4.6
OUT
for normal operation.
= 3.3V
5.1
R
TOFF
130
100
39
56
75
82
39
51
62
5.6
(kΩ)