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PDF MAX1712 Data sheet ( Hoja de datos )
| Número de pieza | MAX1712 | |
| Descripción | High-Speed / Digitally Adjusted Step-Down Controllers for Notebook CPUs | |
| Fabricantes | Maxim Integrated | |
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Hay una vista previa y un enlace de descarga de MAX1712 (archivo pdf) en la parte inferior de esta página. Total 28 Páginas | ||
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19-4781; Rev 1; 7/00
EVAALVUAAILTAIOBNLEKIT
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
General Description
The MAX1710/MAX1711 step-down controllers are
intended for core CPU DC-DC converters in notebook
computers. They feature a triple-threat combination of
ultra-fast transient response, high DC accuracy, and
high efficiency needed for leading-edge CPU core
power supplies. Maxim’s proprietary Quick-PWM™
quick-response, constant-on-time PWM control scheme
handles wide input/output voltage ratios with ease and
provides 100ns “instant-on” response to load transients
while maintaining a relatively constant switching fre-
quency.
High DC precision is ensured by a 2-wire remote-sens-
ing scheme that compensates for voltage drops in both
the ground bus and supply rail. An on-board, digital-to-
analog converter (DAC) sets the output voltage in com-
pliance with Mobile Pentium II® CPU specifications.
The MAX1710 achieves high efficiency at a reduced
cost by eliminating the current-sense resistor found in
traditional current-mode PWMs. Efficiency is further
enhanced by an ability to drive very large synchronous-
rectifier MOSFETs.
Single-stage buck conversion allows these devices to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, 2-stage conversion
(stepping down the +5V system supply instead of the
battery) at a higher switching frequency allows the mini-
mum possible physical size.
The MAX1710/MAX1711 are identical except that the
MAX1711 have 5-bit DACs and the MAX1710 has a 4-
bit DAC. Also, the MAX1711 has a fixed overvoltage
protection threshold at VOUT = 2.25V and undervoltage
protection at VOUT = 0.8V whereas the MAX1710 has
variable thresholds that track VOUT. The MAX1711 is
intended for applications where the DAC code may
change dynamically.
Applications
Notebook Computers
Docking Stations
CPU Core DC-DC Converters
Single-Stage (BATT to VCORE) Converters
Two-Stage (+5V to VCORE) Converters
Quick-PWM is a trademark of Maxim Integrated Products.
Mobile Pentium II is a registered trademark of Intel Corp.
Pin Configurations appear at end of data sheet.
Features
o Ultra-High Efficiency
o No Current-Sense Resistor (Lossless ILIMIT)
o Quick-PWM with 100ns Load-Step Response
o ±1% VOUT Accuracy over Line and Load
o 4-Bit On-Board DAC (MAX1710)
o 5-Bit On-Board DAC (MAX1711/MAX1712)
o 0.925V to 2V Output Adjust Range
(MAX1711/MAX1712)
o 2V to 28V Battery Input Range
o 200/300/400/550kHz Switching Frequency
o Remote GND and VOUT Sensing
o Over/Undervoltage Protection
o 1.7ms Digital Soft-Start
o Drive Large Synchronous-Rectifier FETs
o 2V ±1% Reference Output
o Power-Good Indicator
o Small 24-Pin QSOP Package
Ordering Information
PART
MAX1710EEG
MAX1711EEG
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 QSOP
24 QSOP
Minimal Operating Circuit
+5V INPUT
BATTERY
4.5V TO 28V
VCC OVP*
SHDN
FBS
ILIM
GNDS
VDD
V+
BST
DH
MAX1710
MAX1711
REF MAX1712 LX
CC
D0
D/A
INPUTS
D1
D2
D3
*MAX1710 ONLY
D4** GND
**MAX1711/MAX1712 ONLY
DL
PGND
FB
SKIP
OUTPUT
0.925V TO 2V
(MAX1711/MAX1712)
________________________________________________________________ Maxim Integrated Products 1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VBATT = 15V, VCC = VDD = 5V, SKIP = GND, TA = -40°C to +85°C, unless otherwise noted.) (Note 3)
PARAMETER
CONDITIONS
MIN TYP MAX
PGOOD Trip Threshold
Measured at FB with respect to unloaded output voltage,
falling edge, hysteresis = 1%
-8.5
-2.5
PGOOD Output Low Voltage
PGOOD Leakage Current
ISINK = 1mA
High state, forced to 5.5V
0.4
1
UNIT
%
V
µA
Note 2: On-Time and Off-Time specifications are measured from 50% point to 50% point at the DH pin with LX forced to 0V, BST
forced to 5V, and a 250pF capacitor connected from DH to LX. Actual in-circuit times may differ due to MOSFET switching
speeds.
Note 3: Specifications from -40°C to 0°C are guaranteed but not production tested.
__________________________________________Typical Operating Characteristics
(7A CPU supply circuit of Figure 1, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(VO = 2.0V, f = 300kHz)
100
VIN = 4.5V
90
80
VIN = 7V
70 VIN = 15V
60 VIN = 24V
50
EFFICIENCY vs. LOAD CURRENT
(VO = 1.6V, f = 300kHz)
100
VIN = 4.5V
90 VIN = 7V
80
70 VIN = 15V
60 VIN = 24V
50
EFFICIENCY vs. LOAD CURRENT
(VO = 1.3V, f = 300kHz)
100
VIN = 4.5V
90
VIN = 7V
80
70
VIN = 15V
60
VIN = 24V
50
40
0.01
0.1 1
LOAD CURRENT (A)
10
EFFICIENCY vs. LOAD CURRENT
(VO = 1.6V, f = 550kHz)
100
VIN = 4.5V
90
VIN = 7V
80
70
VIN = 15V
60
50
40
0.01
VIN = 24V
0.1 1
LOAD CURRENT (A)
10
40
0.01
0.1 1
LOAD CURRENT (A)
10
FREQUENCY vs. LOAD CURRENT
(VO = 1.6V)
350
300
VIN = 15V, PWM MODE
250
200 VIN = 4.5V, SKIP MODE
150
VIN = 15V, SKIP MODE
100
50
0
0.01
TON = OPEN
0.1 1
LOAD CURRENT (A)
10
40
0.01
0.1 1
LOAD CURRENT (A)
10
FREQUENCY vs. INPUT VOLTAGE
(IO = 7A)
320
318
316
314
312
VO = 2.0V
310
VO = 1.6V
308
306
304
302 TON = OPEN
300
0
5 10 15 20 25 30
INPUT VOLTAGE (V)
_______________________________________________________________________________________ 5
5 Page 
High-Speed, Digitally Adjusted
Step-Down Controllers for Notebook CPUs
VBATT 2V TO 28V
RLIM
V+ ILIM
TON ON-TIME FROM
COMPUTE D/A
TOFF
1-SHOT
Q TRIG
VCC
5µA
TON
TRIG Q
1-SHOT
SQ
R
OVP
SKIP
SHDN
CC
REF
70k
ERROR
AMP
10k
REF
gm
GNDS
FBS
REF
-5%
gm gm
FB
REF
+12%
REF
-30%
CURRENT
LIMIT
Σ
S
Q
R
PGOOD
S1
S2
Q
OVP/UVLO
LATCH
TIMER
R-2R
D/A CONVERTER
D0 D1 D2 D3
MAX1710
+5V
BST
DH
LX
ZERO CROSSING
VDD +5V
DL
PGND
FB
CHIP SUPPLY VCC
2V REF
REF
GND
+5V
OUTPUT
Figure 2. MAX1710 Functional Diagram
IBIAS = ICC + f ✕ (QG1 + QG2) = 15mA to 30mA (typ)
where ICC is 600µA (typ), f is the switching frequency,
and QG1 and QG2 are the MOSFET data sheet total
gate-charge specification limits at VGS = 5V.
Free-Running, Constant-On-Time PWM
Controller with Input Feed-Forward
The Quick-PWM control architecture is an almost fixed-
frequency, constant-on-time current-mode type with volt-
age feed-forward (Figure 2). This architecture relies on
the filter capacitor’s ESR to act as the current-sense
resistor, so the output ripple voltage provides the PWM
ramp signal. The control algorithm is simple: the high-
side switch on-time is determined solely by a one-shot
whose period is inversely proportional to input voltage
and directly proportional to output voltage. Another one-
shot sets a minimum off-time (400ns typ). The on-time
one-shot is triggered if the error comparator is low, the
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet MAX1712.PDF ] | |
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