MAX1638EAG+ Maxim Integrated Products, MAX1638EAG+ Datasheet - Page 9

• Manufacturer Part Number: MAX1638EAG+
• Description: IC STEP-DWN CTRLR HI-SPD 24-SSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1638EAG+

• Applications: Controller, Intel Pentium® II
• Voltage - Input: 4.5 ~ 5.5 V
• Number Of Outputs: 1
• Voltage - Output: 1.3 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SSOP
• Output Voltage: 1.3 V to 5.5 V
• Output Current: 35 A
• Input Voltage: 4.5 V to 5.5 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The heart of the current-mode PWM controller is a
multi-input open-loop comparator that sums three sig-
nals (Figure 2): the buffered feedback signal, the cur-
rent-sense signal, and the slope-compensation ramp.
This direct-summing configuration approaches ideal
cycle-by-cycle control over the output voltage. The out-
put voltage error signal is generated by an error ampli-
fier that compares the amplified feedback voltage to an
internal reference.
Each pulse from the oscillator sets the main PWM latch
that turns on the high-side switch for a period deter-
mined by the duty factor (approximately V
The current-mode feedback system regulates the peak
inductor current as a function of the output voltage
error signal. Since average inductor current is nearly
the same as peak current (assuming the inductor value
is set relatively high to minimize ripple current), the cir-
cuit acts as a switch-mode transconductance amplifier.
Note: Parts used in evaluation board are shown in bold.
Table 1. Component List for Standard Applications
COMPONENT
R2 (optional)
(optional)
(optional)
P1/N3
C1
C2
D1
D2
N1
N2
R1
L1
PWM Controller Block and Integrator
Synchronous Rectification for CPU Power
(x2) Dale WSL-2512-R009-F (10mΩ)
Central Semiconductor CMPSH-3
Int’l Rectifier IRF7105 (0.4Ω/0.16Ω)
_______________________________________________________________________________________
(x3) Sanyo OS-CON 10SA220M
Dale WSL-2512-R120-J (120mΩ)
Fairchild FDB7030L (10mΩ) or
Fairchild FDB7030L (10mΩ) or
(x4) Sanyo OS-CON 4SP220M
Int’l Rectifier IRL3803S (9mΩ)
Int’l Rectifier IRL3803S (9mΩ)
(0.70µH, 19A, 1.6mΩ, SMD)
diode or Motorola MBRS340
Nihon NSQ03A02 Schottky
Panasonic ETQP1F0R7H
(0.47μH, 19A, SMD) or
High-Speed Step-Down Controller with
Coiltronics UP4-R47
2.0V, 14A
(220μF)
(220μF)
OUT
/ V
Int’l Rectifier IRF7307 (0.09Ω/0.05Ω)
(x2) Fairchild FDB7030L (10mΩ) or
(x2) Fairchild FDB7030L (10mΩ) or
(x2) Dale WSR-20.007 ±1% (7mΩ)
(x2) Int’l Rectifier IRL3803S (9mΩ)
(x2) Int’l Rectifier IRL3803S (9mΩ)
Central Semiconductor CMPSH-3
(x4) Sanyo/OS-CON 10SA220M
IN
(x6) Sanyo OS-CON 4SP220M
(0.70µH, 23A, 0.94mΩ, SMD)
).
diode or Motorola MBRS340
Nihon NSQ03A02 Schottky
Panasonic ETQP2F1R0S
LOAD REQUIREMENT
It pushes the second output LC filter pole, normally
found in a duty-factor-controlled (voltage-mode) PWM,
to a higher frequency. To preserve inner-loop stability
and eliminate regenerative inductor current staircasing,
a slope-compensation ramp is summed into the main
PWM comparator. Under fault conditions where the
inductor current exceeds the maximum current-limit
threshold, the high-side latch resets, and the high-side
switch turns off.
The internal 3.5V reference (REF) is accurate to ±1%
from 0°C to +85°C, making REF useful as a system ref-
erence. Bypass REF to AGND with a 0.1µF (min)
ceramic capacitor. A larger value (such as 2.2µF) is
recommended for high-current applications. Load reg-
ulation is 10mV for loads up to 100µA. Reference
undervoltage lockout is between 2.7V and 3V. Short-
circuit current is less than 4mA.
2.0V, 19A
(220µF)
(220µF)
—
Int’l Rectifier IRF7307 (0.09Ω/0.05Ω)
(x2) Fairchild FDB7030L (10mΩ) or
(x2) Fairchild FDB7030L (10mΩ) or
(x2) Dale WSR-20.007 ±1% (7mΩ)
(x2) Int’l Rectifier IRL3803S (9mΩ)
(x2) Int’l Rectifier IRL3803S (9mΩ)
Central Semiconductor CMPSH-3
(x4) Sanyo/OS-CON 10SA220M
(x7) Sanyo OS-CON 4SP220M
(0.70µH, 23A, 0.94mΩ, SMD)
diode or Motorola MBRS340
Nihon NSQ03A02 Schottky
Panasonic ETQP2F1R0S
Internal Reference
1.3V, 19A
(220µF)
(220µF)
—
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