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MAX1802EHJMAXIMN/a4513avaiDigital Camera Step-Down Power Supply


MAX1802EHJ ,Digital Camera Step-Down Power SupplyApplicationsPART TEMP. RANGE PIN-PACKAGEDigital Still CamerasMAX1802EHJ -40°C to +85°C 32 TQFPDigit ..
MAX1802EHJ+ ,Digital Camera Step-Down Power SupplyApplicationsPART TEMP. RANGE PIN-PACKAGEDigital Still CamerasMAX1802EHJ -40°C to +85°C 32 TQFPDigit ..
MAX1802EHJ+T ,Digital Camera Step-Down Power SupplyELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V = 6V, V = 3V, PGNDM = PGND = GND, DCON1 = REF, V ..
MAX1805MEE ,Multichannel Remote/Local Temperature SensorsELECTRICAL CHARACTERISTICS(V = +3.3V, STBY = V , configuration byte = X0XXXX00, T = 0°C to +125°C, ..
MAX1806EUA08 ,500mA, Low-Voltage Linear Regulator in UMAXfeatures include an active-low, power-OK output Thermal Overload Protectionthat indicates when the ..
MAX1806EUA08+T ,500mA, Low-Voltage Linear Regulator in µMAXELECTRICAL CHARACTERISTICS(V = V + 500mV or V = +2.25V whichever is greater, SET = GND, SHDN = IN, ..
MAX4659EUA+ ,High-Current, 25Ω, SPDT, CMOS Analog SwitchesApplicationsPin ConfigurationRelay Replacement Test EquipmentTOP VIEWCommunication SystemsxDSL Mode ..
MAX465CNG ,Two-Channel, Triple/Quad RGB Video Switches and BuffersApplicationsV- 6 19 V-Broadcast-Quality Color-Signal MultiplexingV- 7 18 OUT0RGB MultiplexingIN0B 8 ..
MAX465CNG ,Two-Channel, Triple/Quad RGB Video Switches and BuffersApplicationsV- 6 19 V-Broadcast-Quality Color-Signal MultiplexingV- 7 18 OUT0RGB MultiplexingIN0B 8 ..
MAX465CWG ,Two-Channel, Triple/Quad RGB Video Switches and BuffersMAX463–MAX47019-0219; Rev 2; 6/94Two-Channel, Triple/QuadRGB Video Switches and Buffers____________ ..
MAX4660ESA ,High-Current / 25 / SPDT / CMOS Analog SwitchesMAX4659/MAX466019-2046; Rev 0; 4/01High-Current, 25Ω , SPDT, CMOSAnalog Switches
MAX4660EUA+T ,High-Current, 25Ω, SPDT, CMOS Analog SwitchesELECTRICAL CHARACTERISTICS—Dual Supplies(V+ = +15V, V- = -15V, V = 2.4V, V = 0.8V, T = T to T , unl ..


MAX1802EHJ
Digital Camera Step-Down Power Supply
General Description
The MAX1802 provides a complete power-supply solu-
tion for digital still cameras and video cameras by inte-
grating two high-efficiency step-down DC-DC converters
and three auxiliary step-up controllers. This complete
solution is targeted for applications that use either three
to four alkaline cells or two lithium-ion (Li+) cells.
The main step-down DC-DC controller accepts inputs
from 2.5V to 11V and regulates a resistor-adjustable out-
put from 2.7V to 5.5V. It uses a synchronous rectifier to
regulate the output with up to 94% efficiency. An
adjustable operating frequency (up to 1MHz) facilitates
designs for optimum size, cost, and efficiency.
The core step-down DC-DC converter accepts inputs
from 2.7V to 5.5V and regulates a resistor-adjustable
output from 1.25V to 5.5V. It delivers 500mA with up to
94% efficiency.
The three auxiliary step-up controllers can be used to
power the digital camera’s CCD, LCD, and backlight.
The MAX1802 also features expandability by supplying
power, an oscillator signal, and a reference to the
MAX1801, a low-cost slave DC-DC controller that sup-
ports step-up, single-ended primary inductance con-
verter (SEPIC), and fly-back configurations.
The MAX1802 is available in a space-saving 32-pin
TQFP package (5mm x 5mm body), and the MAX1801
is available in an 8-pin SOT-23 package. An evaluation
kit (MAX1802EVKIT) featuring both devices is available
to expedite designs.
________________________Applications

Digital Still Cameras
Digital Video Cameras
Hand-Held Devices
Internet Access Tablets
PDAs
DVD Players
Features
2.5V to 11V Input Voltage Range Main DC-DC Controller
94% Efficiency
+2.7V to +5.5V Adjustable Output Voltage
Up to 100% Duty Cycle
Independent Shutdown
Core DC-DC Converter
94% Efficiency
Up to 500mA Load Efficiency
Output Voltage Adjustable Down to 1.25V
Independent Shutdown
Three Auxiliary DC-DC Controllers
Adjustable Maximum Duty Cycle
Independent Shutdown
Power, Oscillator, and Reference Outputs to Drive
External Slave Controllers (MAX1801)
Up to 1MHz Switching Frequency3µA Supply Current in Shutdown ModeInternal Soft-Start Overload Protection for All DC-DC ConvertersCompact 32-Pin TQFP Package
MAX1802
Digital Camera Step-Down
Power Supplyypical Operating Circuit

19-1850; Rev 0; 10/00
Ordering Information
Note:
Refer to the separate data sheet for MAX1801EKA in an 8-
pin SOT.
Pin Configuration appears at end of data sheet.
MAX1802
Digital Camera Step-Down
Power Supply
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, VVDDM= 6V, VVDDC= 3V, PGNDM = PGND = GND, DCON1 = REF, VONM= 3V, VONC= VON1= VDCON2=
VDCON3= 0, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
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.
VDDM, VH, ONM to GND.......................................-0.3V to +12V
PGNDM, PGND to GND........................................-0.3V to +0.3V
VH to VDDM.............................................................-6V to +0.3V
VL to VDDM............................................................-12V to +0.3V
VL, ONC, ON1, FB_, DCON_ to GND......................-0.3V to +6V
VDDC, REF, OSC, COMP_ to GND..............-0.3V to (VL + 0.3V)
DHM, DLM to PGNDM............................-0.3V to (VDDM + 0.3V)
LXM to PGNDM......................................-0.6V to (VDDM + 0.6V)
DL1, DL2, DL3, LXC to PGND................-0.3V to (VDDC + 0.3V)
Continuous Power Dissipation (TA= +70°C)
32-Pin TQFP (derate 11.1mW/°C above +70°C)........889mW
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
MAX1802
Digital Camera Step-Down
Power Supply
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VVDDM= 6V, VVDDC= 3V, PGNDM = PGND = GND, DCON1 = REF, VONM= 3V, VONC= VON1= VDCON2=
VDCON3= 0, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
Idle Mode is a trademark of Maxim Integrated Products.
MAX1802
Digital Camera Step-Down
Power Supply
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VVDDM= 6V, VVDDC= 3V, PGNDM = PGND = GND, DCON1 = REF, VONM= 3V, VONC= VON1= VDCON2=
VDCON3= 0, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
MAX1802
Digital Camera Step-Down
Power Supply
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VVDDM= 6V, VVDDC= 3V, PGNDM = PGND = GND, DCON1 = REF, VONM= 3V, VONC= VON1= VDCON2=
VDCON3= 0, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
MAX1802
Digital Camera Step-Down
Power Supply
ELECTRICAL CHARACTERISTICS

(Circuit of Figure 1, VVDDM= 6V, VVDDC= 3V, PGNDM = PGND = GND, DCON1 = REF, VONM= 3V, VONC= VON1= VDCON2=
VDCON3= 0, TA = -40°C to +85°C, unless otherwise noted.) (Note 1)
MAX1802
Digital Camera Step-Down
Power Supply
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VVDDM= 6V, VVDDC= 3V, PGNDM = PGND = GND, DCON1 = REF, VONM= 3V, VONC= VON1= VDCON2=
VDCON3= 0, TA = -40°C to +85°C,unless otherwise noted.) (Note 1)
MAX1802
Digital Camera Step-Down
Power Supply
ELECTRICAL CHARACTERISTICS (continued)

(Circuit of Figure 1, VVDDM= 6V, VVDDC= 3V, PGNDM = PGND = GND, DCON1 = REF, VONM= 3V, VONC= VON1= VDCON2=
VDCON3= 0, TA = -40°C to +85°C,unless otherwise noted.) (Note 1)
MAX1802
Digital Camera Step-Down
Power Supply
1001000
MAX1802 toc03
Typical Operating Characteristics

(Circuit of Figure 1, VVDDM = 6V, VVDDC= 3.3V, VONM = 3V, VONC= VON1= VDCON2= VDCON3= 0, TA = +25°C, unless otherwise
noted.)
MAX1802
Digital Camera Step-Down
Power Supply
Typical Operating Characteristics (continued)

(Circuit of Figure 1, VVDDM = 6V, VVDDC= 3.3V, VONM = 3V, VONC= VON1= VDCON2= VDCON3= 0, TA = +25°C, unless otherwise
noted.)
MAX1802
Digital Camera Step-Down
Power Supply
Typical Operating Characteristics (continued)

(Circuit of Figure 1, VVDDM = 6V, VVDDC= 3.3V, VONM = 3V, VONC= VON1= VDCON2= VDCON3= 0, TA = +25°C, unless otherwise
noted.)
MAX1802
Digital Camera Step-Down
Power Supply
Pin Description
MAX1802
Digital Camera Step-Down
Power Supply
MAX1802
Digital Camera Step-Down
Power Supply
Detailed Description

The MAX1802 typical application circuit is shown in
Figure 1. It features two step-down DC-DC converters
(main and core), three auxiliary step-up DC-DC con-
trollers, and control capability for multiple external
MAX1801 slave DC-DC controllers. Together, these
provide a complete high-efficiency power-supply solu-
tion for digital still cameras. Figures 2 and 3 show the
MAX1802 functional block diagrams.
Master-Slave Configuration

The MAX1802 supports MAX1801 “slave” controllers
that obtain input power, a voltage reference, and an
oscillator signal directly from the MAX1802 “master”
DC-DC converter. The master-slave configuration
reduces system cost by eliminating redundant circuitry
and controlling the harmonic content of noise with syn-
chronized converter switching.
Main DC-DC Converter

The MAX1802 main step-down DC-DC converter gen-
erates a 2.7V to 5.5V output voltage from a 2.5V to 11V
battery input voltage. When the battery voltage is lower
than the main regulation voltage, the regulator goes
into dropout and the P-channel switch remains on. In
this condition, the output voltage is slightly lower than
the input voltage. The converter drives an external P-
channel MOSFET power switch and an external N-
channel MOSFET synchronous rectifier. The converter
operates in a low-noise, constant-frequency PWM cur-
rent mode to regulate the voltage across the load.
Switching harmonics generated by fixed-frequency
operation are consistent and easily filtered.
The external P-channel MOSFET switch turns on during
the first part of each cycle, allowing current to ramp up
in the inductor and store energy in a magnetic field
while supplying current to the load. During the second
part of each cycle, the P-channel MOSFET turns off and
the voltage across the inductor reverses, forcing cur-
rent through the external N-channel synchronous rectifi-
er to the output filter capacitor and load. As the energy
stored in the inductor is depleted, the current ramps
down. The synchronous rectifier turns off when the
inductor current approaches zero or at the beginning of
a new cycle, at which time the P-channel switch turns
on again.
The current-mode PWM converter uses the voltage at
COMPM to program the inductor current and regulate
the output voltage. The converter detects inductor cur-
rent by sensing the voltage across the source and
drain of the external P-channel MOSFET. The MAX1802
main output switches to Idle Mode at light loads to
improve efficiency by leaving the P-channel switch on
until the voltage across the MOSFET reaches the 20mV
Idle Mode threshold. The Idle Mode current is 20mV
divided by the MOSFET on-resistance. By forcing the
inductor current above the Idle Mode threshold, more
energy is supplied to the output capacitor than is
required by the load. The switch and synchronous rec-
tifiers then remain off until the output capacitor dis-
charges to the regulation voltage. This causes the
converter to operate at a lower effective switching fre-
quency at light loads, thus improving efficiency.
An internal comparator turns off the N-channel synchro-
nous rectifier as the inductor current drops near zero,
by measuring the voltage across the MOSFET. If the N-
channel MOSFET on-resistance is low (less than that of
the P-channel switch), it may cause the MOSFET to turn
off prematurely, degrading efficiency. This is especially
critical for high input voltage applications, such as with
2 series Li+ cells. In this case, use an N-channel MOS-
FET with greater on-resistance than the P-channel
switch, and/or place a Schottky recitifier across the N-
channel MOSFET gate-source.
The voltage at COMPM is typically clamped to
VCOMPM(MAX)= 2.14V, thereby limiting the inductor
current. The peak inductor current (ILIM) and the maxi-
mum average output current (IOUT(MAX)) are deter-
mined by the following equations:
where AVSWMis the main slope compensation gain
(0.20V/V), AVCSMis the voltage gain of the main cur-
rent-sense amplifier (9.3V/V), RDSPis the on-resistance
of the external P-channel MOSFET switch, and L is the
inductor value. Note that the current limit increases as
the input/output voltage ratio increases.
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