MAX6841IUKD4+T Maxim Integrated, MAX6841IUKD4+T Datasheet - Page 12

• Manufacturer Part Number: MAX6841IUKD4+T
• Description: Supervisory Circuits
• Manufacturer: Maxim Integrated
• Series: MAX6841, MAX6842, MAX6843, MAX6844, MAX6845r

Specifications of MAX6841IUKD4+T

• Number Of Voltages Monitored: 1
• Monitored Voltage: 0.9 V to 1.5 V
• Undervoltage Threshold: 1.35 V
• Overvoltage Threshold: 1.425 V
• Output Type: Active High, Active Low, Push-Pull
• Manual Reset: Resettable
• Watchdog: No Watchdog
• Battery Backup Switching: No Backup
• Power-up Reset Delay (typ): 2240 ms
• Supply Voltage - Max: 1.8 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOT-23
• Chip Enable Signals: No
• Maximum Power Dissipation: 571 mW
• Minimum Operating Temperature: - 40 C
• Power Fail Detection: No
• Supply Current (typ): 8.1 uA
• Supply Voltage - Min: 0.75 V

Two-Phase Desktop CPU Core Supply
Controllers with Controlled VID Change
The MAX1937/MAX1938/MAX1939 is a family of syn-
chronous, two-phase step-down controllers capable of
delivering load currents up to 60A. The controllers use
Quick-PWM control architecture in conjunction with
active load current voltage positioning. Quick-PWM
control provides instantaneous load-step response,
while programmable voltage positioning allows the con-
verter to utilize full transient regulation limits, reducing
the output capacitance requirement. Furthermore, the
two phases operate 180° out-of-phase with an effective
500kHz switching frequency, thus reducing input and
output current ripple, as well as reducing input filter
capacitor requirements.
The MAX1937/MAX1938/MAX1939 are compliant with
the AMD Hammer, Intel VRM 9.0/VRM 9.1, and AMD
Athlon Mobile VID code specifications (see Table 1 for
VID codes). The internal DAC provides ultra-high accu-
racy of ±0.75%. A controlled VID voltage transition is
implemented to minimize both undervoltage and over-
voltage overshoot during VID input change.
Remote sensing is available for high output-voltage
accuracy. The MOSFET switches are driven by with a
6V gate-drive circuit to minimize switching and
crossover conduction losses to achieve efficiency as
high as 90%. The MAX1937/MAX1938/ MAX1939 fea-
ture cycle-by-cycle current limit to ensure current limit
is not exceeded. Crowbar protection is available to pro-
tect against output overvoltage.
12
______________________________________________________________________________________
PIN
22
23
24
25
26
27
28
NAME
BST1
DH1
VLG
CS1
V
DL1
LX1
CC
Detailed Description
DL_ Driver Power-Supply Input. Connect to a 4.5V to 6.5V supply for powering the low-side MOSFET
gate drive, and the bootstrap circuit for driving the high-side MOSFETs. Ensure that V
than or equal to V
Low-Side MOSFET Gate-Driver Output. Connect to the low-side MOSFET gate. DL1 is pulled low in
shutdown.
Negative Current-Sense Input. Connect to a current-sense resistor in series with the low-side
MOSFET or connect to LX1 to use the low-side MOSFET’s on-resistance for current sensing.
Inductor Connection. Connect to the switched side of the inductor.
High-Side MOSFET Gate-Drive Output. Connect to the high-side MOSFET gate. DH1 is pulled low in
shutdown.
High-Side MOSFET Gate-Driver Bootstrap Input. Connect 0.22µF or higher value bypass capacitor
from BST1 to LX1. Keep trace length as short as possible. Connect a Schottky diode between BST1
and VLG. See the Selecting a BST Capacitor section.
Input Voltage Sense. Connect to the input supply at the high-side MOSFET drain. The voltage
sensed at V
CC
is used to set the on-time.
VDD
.
The heart of the Quick-PWM core is the one-shot that
sets the high-side switch on-time. This fast, low-jitter,
one-shot circuitry varies the on-time in response to the
input and output voltages. The high-side switch on-time
is inversely proportional to the voltage applied to V
and directly proportional to the output voltage. This
algorithm results in a nearly constant switching fre-
quency, despite the lack of a fixed-frequency clock
generator. The benefits of a constant switching fre-
quency are twofold: the frequency selected avoids
noise-sensitive regions, and the inductor ripple current
operating point remains relatively constant, resulting in
easy design methodology and predictable output volt-
age ripple:
where the constant K is 4µs and V
drop across the low-side MOSFET’s on-resistance plus
the drop across the current-sense resistor (V
75mV), if used.
The on-time one-shot has good accuracy at the operat-
ing point specified in the Electrical Characteristics. On-
times at operating points far removed from the
conditions specified in the Electrical Characteristics can
vary over a wide range. For example, the regulators run
slower with input voltages greater than 12V because of
the very short on-times required.
FUNCTION
Pin Description (continued)
t
ON
=
K V
(
OUT
V
VCC
+
V
On-Time One-Shot
DROP
DROP
)
VLG
is the voltage
is greater
DROP
CC
≈