MAX1844ETP+ Maxim Integrated Products, MAX1844ETP+ Datasheet - Page 10

• Manufacturer Part Number: MAX1844ETP+
• Description: IC CNTRLR STP DWN HS 20-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX1844ETP+

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.8V, 2.5V, Adj
• Current - Output: 4A
• Frequency - Switching: 200kHz, 300kHz, 450kHz, 600kHz
• Voltage - Input: 2 ~ 28 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-TQFN Exposed Pad
• Power - Output: 727mW
• Output Voltage: 1 V to 5.5 V, 1.8 V, 2.5 V
• Output Current: 4000 mA
• Mounting Style: SMD/SMT
• Switching Frequency: 600 KHz
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Synchronous Pin: No
• Topology: Buck
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX1844 buck controller is targeted for low-voltage
power supplies for notebook computers. Maxim’s propri-
etary Quick-PWM pulse-width modulator in the MAX1844
is specifically designed for handling fast load steps while
maintaining a relatively constant operating frequency
and inductor operating point over a wide range of input
voltages. The Quick-PWM architecture circumvents the
poor load-transient timing problems of fixed-frequency
current-mode PWMs while also avoiding the problems
caused by widely varying switching frequencies in con-
ventional constant-on-time and constant-off-time PWM
schemes.
High-Speed Step-Down Controller with
Accurate Current Limit for Notebook Computers
Figure 1. Standard Application Circuit
10
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SEE TABLE 1 FOR OTHER COMPONENT SELECTIONS.
Detailed Description
BIAS SUPPLY
LOW-NOISE
7V TO 20V
CONTROL
CONTROL
130kΩ
270kΩ
V
ON/OFF
IN
5V
C4
0.22µF
4.7µF
C5
V+
SHDN
SKIP
ILIM
TON
REF
GND
V
UVP
CC
MAX1844
20Ω
R1
PGOOD
LATCH
V
OVP
OUT
BST
DD
DH
CS
LX
DL
FB
The MAX1844 requires an external 5V bias supply in
addition to the battery. Typically, this 5V bias supply is
the notebook’s 95% efficient 5V system supply. Keeping
the bias supply external to the IC improves efficiency
and eliminates the cost associated with the 5V linear reg-
ulator that would otherwise be needed to supply the
PWM circuit and gate drivers. If stand-alone capability is
needed, the 5V supply can be generated with an exter-
nal linear regulator such as the MAX1615.
The battery and 5V bias inputs can be connected
together if the input source is a fixed 4.5V to 5.5V supply.
If the 5V bias supply is powered up prior to the
5V
C7
0.1µF
R2
100kΩ
D2
CMPSH-3
3.3µF
C6
POWER-GOOD
INDICATOR
Q1
Q2
R
15mΩ
10µF
SENSE
C1
5V Bias Supply (V
4.7µH
L1
D1
C2
330µF
V
2.5V
OUT
CC
and V
DD
)