MAX1639ESE Maxim Integrated Products, MAX1639ESE Datasheet - Page 7

• Manufacturer Part Number: MAX1639ESE
• Description: DC/DC Switching Controllers
• Manufacturer: Maxim Integrated Products

Specifications of MAX1639ESE

• Number Of Outputs: 1
• Output Voltage: 1.1 V to 4.5 V
• Input Voltage: 4.5 V to 5.5 V
• Mounting Style: SMD/SMT
• Package / Case: SOIC-16
• 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
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 rela-
tively high to minimize ripple current), the circuit acts as
a switch-mode transconductance amplifier. It pushes the
second output LC filter pole, normally found in a duty-
factor-controlled (voltage-mode) PWM, to a higher fre-
quency. To preserve inner-loop stability and eliminate
regenerative inductor current staircasing, a slope-
compensation ramp is summed into the main PWM com-
parator. Under fault conditions where the inductor cur-
rent exceeds the maximum current-limit threshold, the
high-side latch resets, and the high-side switch turns off.
Table 1. Component List for Standard Applications
Note: Parts used in evaluation board are shown in bold.
COMPONENT
D1 (optional)
PWM Controller Block and Integrator
C1
C2
D2
N1
N2
L1
R1
R7
R8
Synchronous Rectification for CPU Power
_______________________________________________________________________________________
High-Speed Step-Down Controller with
(x2) 560µF, Sanyo OS-CON 4SP560M
Central Semiconductor CMPSH-3
330µF, Sanyo OS-CON 6SA330M
Schottky diode, Nihon NSQ03A02
International Rectifier IRF7413
International Rectifier IRF7413
Coilcraft D03316P-102HC
Coiltronics UP2B-1R0
Fairchild FDS6680
Fairchild FDS6680
WSL-2512-R009-J
1.0µH, 9.3A, SMD
0.014Ω, 30V, SO8
0.014Ω, 30V, SO8
0.018Ω, 30V, SO8
0.018Ω, 30V, SO8
1.0µH, 10A, SMD
OUT
10.0kΩ, 1%
12.7kΩ, 1%
9mΩ Dale,
2.5V, 8A
/ V
IN
). The
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.
Synchronous rectification reduces conduction losses in
the rectifier by shunting the normal Schottky diode or
MOSFET body diode with a low-on-resistance MOSFET
switch. The synchronous rectifier also ensures proper
start-up by precharging the boost-charge pump used
for the high-side switch gate-drive circuit. Thus, if you
must omit the synchronous power MOSFET for cost or
other reasons, replace it with a small-signal MOSFET,
such as a 2N7002.
The DL drive waveform is simply the complement of the
DH high-side drive waveform (with typical controlled
dead time of 30ns to prevent cross-conduction or
shoot-through). The DL output’s on-resistance is 0.7Ω
(typ) and 2
LOAD REQUIREMENT
Ω
(x2) 0.010Ω, 30V, D
(x2) 0.010Ω, 30V, D
(max).
(x2) 0.014Ω, 30V, SO8, Fairchild FDS6680
(x2) 0.014Ω, 30V, SO8, Fairchild FDS6680
(x3) 330µF, Sanyo OS-CON 6SA330M
(x5) 560µF, Sanyo OS-CON 4SP560M
Schottky diode, Motorola MBRD640
(x2) 7mΩ, Dale WSL-2512-R007-J
Synchronous-Rectifier Driver
Central Semiconductor CMPSH-3
Panasonic ETQPAF0R3E
0.3µH, 25A, 0.9mΩ
10.0kΩ, 1%
6.19kΩ, 1%
1.8V, 20A
2
2
PAK, Fairchild FDB7030L
PAK, Fairchild FDB7030L
Internal Reference
7