MAX1864TEEE Fast Delivery |IC PHOENIX CO.,LIMITED

MAX1864TEEE ,xDSL/Cable Modem Triple/Quintuple Output Power SuppliesApplicationsOUT 3 14 BSTxDSL, Cable, and ISDN Modems MAX1864FB 4 13 DHB2 5 12 LXSet-Top BoxesFB2 6 ..
MAX1864TEEE ,xDSL/Cable Modem Triple/Quintuple Output Power Suppliesapplications such Master DC-DC Step-Down Converteras cable modem Consumer Premise Equipment (CPE), ..
MAX1864TEEE+ ,xDSL/Cable Modem Triple/Quintuple Output Power Suppliesapplications such♦ Master DC-DC Step-Down Converteras cable modem Consumer Premise Equipment (CPE), ..
MAX1864TEEE+T ,xDSL/Cable Modem Triple/Quintuple Output Power SuppliesELECTRICAL CHARACTERISTICS(V = 12V, ILIM = FB = GND, V - V = 5V, T = 0°C to +85°C. Typical values a ..
MAX1864TEEE-T ,xDSL/Cable Modem Triple/Quintuple Output Power SuppliesFeaturesThe MAX1864/MAX1865 power-supply controllers are ♦ 4.5V to 28V Input Voltage Rangedesigned ..
MAX186ACAP ,Low-Power, 8-Channel, Serial 12-Bit ADCsFeaturesThe MAX186/MAX188 are 12-bit data-acquisition sys- ' 8-Channel Single-Ended or 4-Channel te ..
MAX4781EUE+ ,High-Speed, Low-Voltage, 0.7Ω CMOS Analog Switches/MultiplexersFeatures♦ On-ResistanceThe MAX4781/MAX4782/MAX4783 are high-speed,0.7Ω (+3V Supply)low-voltage, low ..
MAX4781EUE+T ,High-Speed, Low-Voltage, 0.7Ω CMOS Analog Switches/MultiplexersApplicationsOrdering InformationBattery-Operated EquipmentPART TEMP RANGE PIN-PACKAGEAudio Signal R ..
MAX4782ETE+T ,High-Speed, Low-Voltage, 0.7Ω CMOS Analog Switches/MultiplexersELECTRICAL CHARACTERISTICS—Single +3V Supply(V = +2.7V to +3.6V, GND = 0, V = 1.4V, V = 0.5V, T = T ..
MAX4782EUE+ ,High-Speed, Low-Voltage, 0.7Ω CMOS Analog Switches/MultiplexersApplicationsOrdering InformationBattery-Operated EquipmentPART TEMP RANGE PIN-PACKAGEAudio Signal R ..
MAX4783ETE+ ,High-Speed, Low-Voltage, 0.7Ω CMOS Analog Switches/MultiplexersMAX4781/MAX4782/MAX478319-2522; Rev 3; 2/05High-Speed, Low-Voltage, 0.7Ω CMOS AnalogSwitches/Multip ..
MAX4784EUE ,0.7 M Low-Voltage, Quad 2:1 Analog MultiplexersApplicationsPower RoutingBattery-Powered SystemsOrdering InformationAudio and Video Signal RoutingL ..

MAX1864TEEE
xDSL/Cable Modem Triple/Quintuple Output Power Supplies
General Description
The MAX1864/MAX1865 power-supply controllers are
designed to address cost-conscious applications such
as cable modem Consumer Premise Equipment (CPE),
xDSL CPE, and set-top boxes. Operating off a low-cost,
unregulated DC supply (such as a wall adapter output),
the MAX1864 generates three positive outputs, and the
MAX1865 generates four positive outputs and one neg-
ative output to provide a cost-effective system power
supply.
The MAX1864 includes a current-mode synchronous
step-down controller and two positive regulator gain
blocks. The MAX1865 has one additional positive gain
block and one negative regulator gain block. The main
synchronous step-down controller generates a
high-current output that is preset to 3.3V or adjustable
from 1.236V to 0.8 ✕VINwith an external resistive-
divider. The 100kHz/200kHz operating frequency
allows the use of low-cost aluminum-electrolytic capaci-
tors and low-cost power magnetics. Additionally, the
MAX1864/MAX1865 step-down controllers sense the
voltage across the low-side MOSFET’s on-resistance to
efficiently provide the current-limit signal, eliminating
the need for costly current-sense resistors.
The MAX1864/MAX1865 generate additional supply
rails at low cost. The positive regulator gain blocks use
an external PNP pass transistor to generate low-voltage
rails directly from the main step-down converter (such
as 2.5V or 1.8V from the main 3.3V output) or higher
voltages using coupled windings from the step-down
converter (such as 5V, 12V, or 15V). The MAX1865’s
negative gain block uses an external NPN pass transis-
tor in conjunction with a coupled winding to generate
-5V, -12V, or -15V.
All output voltages are externally adjustable, providing
maximum flexibility. Additionally, the MAX1864/
MAX1865 feature soft-start for the step-down converter
and all the positive linear regulators, and have a power-
good output that monitors all of the output voltages.
Applications
xDSL, Cable, and ISDN Modems
Set-Top Boxes
Wireless Local Loop
Features4.5V to 28V Input Voltage RangeMaster DC-DC Step-Down Converter
Preset 3.3V or Adjustable (1.236V to 0.8 ✕ VIN)
Output Voltage
Fixed-Frequency (100kHz/200kHz) PWM
Controller
No Current-Sense Resistor
Adjustable Current Limit
95% EfficientTwo (MAX1864)/Four (MAX1865) Analog
Gain Blocks
Positive Analog Blocks Drive Low-Cost PNP
Pass Transistors to Build Positive Linear
Regulators
Negative Analog Block (MAX1865) Drives a
Low-Cost NPN Pass Transistor to Build a
Negative Linear RegulatorPower-Good IndicatorSoft-Start Ramp for All Positive Regulators
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
Pin Configurations
Ordering Information
19-2030; Rev 0; 4/01
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= 12V, ILIM = FB = GND, VBST- VLX= 5V, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN, B2, B3, B4 to GND............................................-0.3V to +30V
B5 to OUT...............................................................-20V to +0.3V
VL, POK, FB, FB2, FB3, FB4, FB5 to GND...............-0.3V to +6V
LX to BST..................................................................-6V to +0.3V
BST to GND............................................................-0.3V to +36V
DH to LX....................................................-0.3V to (VBST+ 0.3V)
DL, OUT, COMP, ILIM to GND......................-0.3V to (VL+ 0.3V)
VL Output Current...............................................................50mA
VL Short Circuit to GND...................................................≤100ms
Continuous Power Dissipation (TA= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........666mW
20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 12V, ILIM = FB = GND, VBST- VLX= 5V, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
ELECTRICAL CHARACTERISTICS
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
Note 1:Connect VL to IN for operation with VIN< 5V.
Note 2:See Output Voltage Selectionsection.
Note 3:The internal 5V linear regulator (VL) powers the thermal shutdown block. Shorting VL to GND disables thermal shutdown.
Note 4:Specifications to -40°C are guaranteed by design, not production tested.
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 12V, ILIM = FB = GND, VBST- VLX= 5V, TA= -40°C to +85°C, unless otherwise noted.) (Note 4)
EFFICIENCY vs. LOAD CURRENT
(PRESET MODE)
MAX1864/65 toc01
LOAD CURRENT (A)
EFFICIENCY (%)
OUTPUT VOLTAGE vs. LOAD CURRENT
(PRESET MODE)
MAX1864/65 toc02
LOAD CURRENT (A)
OUTPUT VOLTAGE (V)
EFFICIENCY vs. LOAD CURRENT
(ADJUSTABLE MODE)
MAX1864/65 toc03
LOAD CURRENT (A)
EFFICIENCY (%)
Typical Operating Characteristics
(Circuit of Figure 1, VIN= 12V, VOUT= 3.3V, TA = +25°C, unless otherwise noted.)
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
2µs/div
SWITCHING WAVEFORMS
(STEP-DOWN CONVERTER)
3.35V
1.5A
MAX1864/65 toc07
3.30V
A. VOUT = 3.3V (PRESET), IOUT = 1A, 50mV/div
B. INDUCTOR CURRENT, 500mA/div
C. VLX, 10V/div
VIN = 12V
10V
0.5A
1ms/div
SOFT-START
MAX1864/65 toc08
A. VL, 5V/div
B. VOUT = 3.3V (PRESET), 2V/div
C. INDUCTOR CURRENT, 1A/div
VIN = 0 TO 12V
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN= 12V, VOUT= 3.3V, TA = +25°C, unless otherwise noted.)
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN= 12V, VOUT= 3.3V, TA = +25°C, unless otherwise noted.)
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN= 12V, VOUT= 3.3V, TA = +25°C, unless otherwise noted.)
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
Pin Description
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
Detailed Description
The MAX1864/MAX1865 power-supply controllers pro-
vide system power for cable and xDSL modems. The
main step-down DC-DC controller operates in a cur-
rent-mode pulse-width-modulation (PWM) control
scheme to ease compensation requirements and pro-
vide excellent load- and line-transient response.
The MAX1864 includes two analog gain blocks to regu-
late two additional positive auxiliary output voltages,
and the MAX1865 includes four analog gain blocks to
regulate three additional positive and one negative aux-
iliary output voltages. The positive regulator gain blocks
can be used to generate low-voltage rails directly from
the main step-down converter or higher voltages using
coupled windings from the step-down converter. The
negative gain block can be used in conjunction with a
coupled winding to generate -5V, -12V, or -15V.
DC-DC Controller
The MAX1864/MAX1865 step-down converters use a
pulse-width-modulated (PWM) current-mode control
scheme (Figure 2). An internal transconductance
amplifier establishes an integrated error voltage at the
COMP pin. The heart of the current-mode PWM con-
troller is an open-loop comparator that compares the
integrated voltage-feedback signal against the ampli-
fied current-sense signal plus the slope compensation
ramp. At each rising edge of the internal clock, the
high-side MOSFET turns-on until the PWM comparator
trips or the maximum duty cycle is reached. During this
on-time, current ramps up through the inductor, sourc-
ing current to the output and storing energy in a mag-
netic field. The current-mode feedback system
regulates the peak inductor current as a function of the
output voltage error signal. Since the average inductor
current is nearly the same as the peak inductor current
(assuming that the inductor value is relatively high to
minimize ripple current), the circuit acts as a switch-
mode transconductance amplifier. It pushes the output
LC filter pole, normally found in a voltage-mode PWM,
to a higher frequency. To preserve inner loop stability
and eliminate inductor stair-casing, a slope-compensa-
tion ramp is summed into the main PWM comparator.
During the second-half of the cycle, the high-side MOS-
FET turns off and the low-side N-channel MOSFET turns
on. Now the inductor releases the stored energy as its
current ramps down, providing current to the output.
Therefore, the output capacitor stores charge when the
inductor current exceeds the load current and dis-
charges when the inductor current is lower, smoothing
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
the voltage across the load. Under overload conditions,
when the inductor current exceeds the selected cur-
rent-limit (see Current Limit), the high-side MOSFET is
not turned on at the rising edge of the clock and the
low-side MOSFET remains on to let the inductor current
ramp down.
The MAX1864/MAX1865 operate in a forced-PWM
mode, so even under light loads the controller main-
tains a constant switching frequency to minimize cross-
regulation errors in applications that use a transformer.
The low-side gate-drive waveform is the complement of
the high-side gate-drive waveform, which causes the
inductor current to reverse under light loads.
Current-Sense Amplifier
The MAX1864/MAX1865s’ current-sense circuit ampli-
fies (AV= 5) the current-sense voltage generated by
the high-side MOSFET’s on-resistance (RDS(ON)✕
IINDUCTOR). This amplified current-sense signal and
the internal slope compensation signal are summed
together (VSUM) and fed into the PWM comparator’s
inverting input. The PWM comparator turns-off the high-
side MOSFET when VSUMexceeds the integrated feed-
back voltage (VCOMP). Place the high-side MOSFET no
further than 5mm from the controller, and connect IN
and LX to the MOSFET using Kelvin sense connections
to guarantee current-sense accuracy and improve
stability.
Figure 1. Standard MAX1864 Application Circuit
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
MAX1864/MAX1865
xDSL/Cable Modem Triple/Quintuple Output
Power Supplies
Current-Limit Circuit
The current-limit circuit employs a unique “valley” cur-
rent-limiting algorithm that uses the low-side MOSFET’s
on-resistance as a sensing element (Figure 3). If the
voltage across the low-side MOSFET (RDS(ON)✕IIN-
DUCTOR) exceeds the current-limit threshold at the
beginning of a new oscillator cycle, the MAX1864/
MAX1865 will not turn on the high-side MOSFET. The
actual peak current is greater than the current-limit
threshold by an amount equal to the inductor ripple
current. Therefore, the exact current-limit characteristic
and maximum load capability are a function of the low-
side MOSFET on-resistance, inductor value, input volt-
age, and output voltage. The reward for this uncertainty
is robust, loss-less overcurrent limiting.
In adjustable mode, the current-limit threshold voltage
is 1/5th the voltage seen at ILIM (IVALLEY= 0.2 ✕VILIM).
Adjust the current-limit threshold by connecting a resis-
tive-divider from VL to ILIM to GND. The current-limit
threshold can be set from 106mV to 530mV, which cor-
responds to ILIM input voltages of 500mV to 2.5V. This
adjustable current limit accommodates MOSFETs with
a wide range of on-resistance characteristics (see
Design Procedure). The current-limit threshold defaults
to 250mV when ILIM is connected to VL. The logic
threshold for switchover to the 250mV default value is
approximately VL - 1V.
Carefully observe the PC board layout guidelines to
ensure that noise and DC errors don’t corrupt the cur-
rent-sense signals seen by LX and GND. The IC must
be mounted close to the low-side MOSFET with short
(less than 5mm), direct traces making a Kelvin sense
connection.
Synchronous Rectifier Driver (DL)
Synchronous rectification reduces conduction losses in
the rectifier by replacing the normal Schottky catch
diode with a low-resistance MOSFET switch. The
MAX1864/MAX1865 also use the synchronous rectifier
to ensure proper startup of the boost gate-driver circuit
and to provide the current-limit signal.
The DL low-side drive waveform is always the comple-
ment of the DH high-side drive waveform (with con-
trolled dead time to prevent cross-conduction or
“shoot-through”). A dead-time circuit monitors the DL
output and prevents the high-side FET from turning on
until DL is fully off. For the dead-time circuit to work
properly, there must be a low-resistance, low-induc-
tance path from the DL driver to the MOSFET gate.
Otherwise, the sense circuitry in the MAX1864/
MAX1865 will interpret the MOSFET gate as “off” when
gate charge actually remains. Use very short, wide
traces (50mil to 100mil wide if the MOSFET is 1 inch
from the device). The dead time at the other edge (DH
turning off) is determined by a fixed internal delay.
High-Side Gate-Drive Supply (BST)
Gate-drive voltage for the high-side N-channel switch is
generated by a flying-capacitor boost circuit (Figure 1).
The capacitor between BST and LX is alternately
charged from the VL supply and placed parallel to the
high-side MOSFET’s gate-source terminals.
On startup, the synchronous rectifier (low-side MOS-
FET) forces LX to ground and charges the boost
capacitor to 5V. On the second half-cycle, the switch-
mode power supply turns on the high-side MOSFET by
closing an internal switch between BST and DH. This
provides the necessary gate-to-source voltage to turn
on the high-side switch, an action that boosts the 5V
gate-drive signal above the battery voltage.
Internal 5V Linear Regulator (VL)
All MAX1864/MAX1865 functions, except the current-
sense amplifier, are internally powered from the on-
chip, low-dropout 5V regulator. The maximum regulator
input voltage (VIN) is 28V. Bypass the regulator’s output
(VL) with at least a 1µF ceramic capacitor to GND. The
VIN-to-VL dropout voltage is typically 200mV, so when
VINis less than 5.2V, VL is typically VIN- 200mV.
The internal linear regulator can source up to 20mA to
supply the IC, power the low-side gate driver, charge
the external boost capacitor, and supply small external
loads. When driving particularly large FETs, little or no
regulator current may be available for external loads.
For example, when switched at 200kHz, a large FET
with 40nC total gate charge requires 40nC x 200kHz,
or 8mA.

Partno	Mfg	Dc	Qty	Available	Descript
MAX1864TEEE	MAX	N/a	2	avai	xDSL/Cable Modem Triple/Quintuple Output Power Supplies
MAX1864TEEE	MAXIM	N/a	1000	avai	xDSL/Cable Modem Triple/Quintuple Output Power Supplies