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MAX1802EHJ+-MAX1802EHJ+T
Digital Camera Step-Down Power Supply
General DescriptionThe 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.
________________________ApplicationsDigital Still Cameras
Digital Video Cameras
Hand-Held Devices
Internet Access Tablets
PDAs
DVD Players
Features2.5V 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 ShutdownCore DC-DC Converter
94% Efficiency
Up to 500mA Load Efficiency
Output Voltage Adjustable Down to 1.25V
Independent ShutdownThree Auxiliary DC-DC Controllers
Adjustable Maximum Duty Cycle
Independent ShutdownPower, 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 Circuit19-1850; 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.32 TQFP
PIN-PACKAGETEMP. RANGE-40°C to +85°CMAX1802EHJ
PARTMAX1802
MASTER
MAX1801
SLAVE
INPUT
2.5V TO 11V
OSCPOWERREF
MOTOR
CORE
MAIN
CCD
CCFL
TFT
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
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSGENERAL Input Voltage Range VIN 2.5 11 V
SUPPLY CURRENT Shutdown Supply Current (from VDDM and VDDC) VONM = 0 3 20 µAVFBM = 1.5V, VVDDC = 0 370 600 Main DC-DC Converter Supply Current (from VDDM) VFBM = 1.5V, VVDDC = 3V 35 55 µAMain DC-DC Converter Supply Current (from VDDC) VFBM = 1.5V, VVDDC = 3V 270 450 µAMain plus Core Supply Current (from VDDC) VFBM = VFBC = 1.5V, VONC = 3V 410 700 µAMain plus Auxiliary 1
Supply Current (from VDDC) VFBM = VFB1 = 1.5V, VON1 = 3V 470 750 µAMain plus Auxiliary 2
Supply Current (from VDDC) VFBM = VFB2 = 1.5V, VDCON2 = 3V 470 750 µAMain plus Auxiliary 3
Supply Current (from VDDC) VFBM = VFB3 = 1.5V, VDCON3 = 3V 470 750 µATotal Supply Current (from VDDC) VFBM = VFBC = VFB1 = VFB2 = VFB3 = 1.5V, VONC = VON1 = VDCON2 = VDCON3 = 3V 960 1700 µA
VL REGULATOR VL Output Voltage 6V < VVDDM < 11V, 0.1mA < ILOAD < 10mA 2.83 3.00 3.12 VVL Supply Rejection 3.5V < VVDDM < 11V, VVDDC = 0 3 %VL Undervoltage Lockout
Threshold VL rising, 40mV hysteresis 2.25 2.40 2.50 VVL Switchover Voltage to
VDDC VL rising, 100mV hysteresis 2.3 2.4 2.5 VVL to VDDC Switch Resistance 7 Ω
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.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSREFERENCE Reference Output Voltage VREF IREF = 20μA 1.235 1.248 1.260 VREF Load Regulation 10μA < IREF < 200μA 5 9 mVREF Line Rejection 2.7V < VOUT < 5.5V 1 5 mVREF Undervoltage Lockout
Threshold REF rising, 20mV hysteresis 0.9 1 1.1 V
OSCILLATOR OSC Discharge Trip Level OSC rising 1.225 1.250 1.275 VOSC Input Bias Current VOSC = 1.1V 0.2 100 nAOSC Discharge Resistance VOSC = 1.5V 30 100 ΩOSC Discharge Pulse Width 100 ns
LOGIC INPUTS (ONM, ONC, ON1) Input Low Level VIL 0.4 VONM 1.8 Input High Level VIH ONC, ON1 1.6 VInput Leakage Current ONM: VIN = 0 or 11V; ONC, ON1: VIN = 0 or 5V 0.01 1 μA
MAIN DC-DC CONVERTER Main Output Voltage Adjust
Range VOUT 2.7 5.5 VMain Idle Mode™ Threshold VOSC = 0.625V, measured between VDDM
and LXM 8 20 32 mVMain Current-Sense Amplifier Voltage Gain AVCSM Measured between VDDM and LXM 8.4 9.3 10.2 V/VMain N Channel Turn-Off
Threshold Measured between LXM and PGNDM -26 -17 -8 mVMain Slope Compensation
Gain AVSWM 0.16 0.20 0.24 V/V
MAIN ERROR AMPLIFIER FBM Regulation Voltage Unity gain configuration, FBM = COMPM 1.233 1.248 1.263 VFBM to COMPM
Transconductance GEA Unity gain configuration, FBM = COMPM,
-5μA < ILOAD < 5μA 70 100 160 μSFBM Input Leakage Current VFBM = 1.35V 5 100 nACOMPM Minimum Output
Voltage VFBM = 1.35V, COMPM open 0.3 VCOMPM Maximum Output
Voltage VCOMPM (MAX) VFBM = 1.15V, COMPM open 2.00 2.14 2.27 V
Idle Mode is a trademark of Maxim Integrated Products.
MAX1802
Digital Camera Step-Down
Power Supply
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSMAIN SOFT-START Soft-Start Interval OSC falling edge 1024 OSC
cycles
MAIN DRIVERS (DHM, DLM) Output Low VoltageISINK = 10mA0.11 V
Output High VoltageISOURCE = 10mAVVDDM -
0.11V
Driver ResistanceIDHM = 10mA, IDLM = 10mA411Ω
Drive CurrentSourcing or sinking,
VDHM or VVL = VVDDM / 2400mA
CORE DC-DC CONVERTER (VONC = 3V) Core Output Voltage Adjust
Range VOUT 1.25 5.5 VCore Idle Mode Threshold VOSC = 0.625V 70 190 320 mACore Current-Sense Amplifier Transresistance RCSC 0.7 1.0 1.3 V/ACore Slope Compensation Gain AVSWC 0.16 0.20 0.24 V/V
CORE ERROR AMPLIFIER (VONC = 3V) FBC Regulation Voltage Unity gain configuration, FBC = COMPC 1.233 1.248 1.263 VFBC to COMPC
Transconductance GEA Unity gain configuration, FBC = COMPC,
-5μA < ILOAD < 5μA 70 100 160 μS
FBC Input Leakage CurrentVFBC = 1.35V5100nA
COMPC Minimum Output
VoltageVFBC = 1.35V, COMPC open0.3V
COMPC Maximum Output
VoltageVCOMPM (MAX)VFBC = 1.15V, COMPC open2.002.142.27V
CORE SOFT-START (VONC = 3V)Soft-Start Interval1024OSC
cycles
CORE POWER SWITCHES (VONC = 3V)LXC Leakage CurrentVLXC = 0, 5.5V0.0120μA
RDSNN-channel, ILXC = 0.75A150350Switch On-ResistanceRDSPP-channel, ILXC = 0.75A180400mΩ
P-Channel Current LimitVOSC = 0.625V0.75A
N-Channel Turn-Off Current18100180mA
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
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSAUXILIARY DC-DC CONTROLLERS 1, 2, 3 (VON1 = VCON_ = 3V) INTERNAL CLOCK OSC Clock Low Trip Level OSC falling edge 0.2 0.25 0.3 VVDCON _ = 0.625V 0.575 0.625 0.675 OSC Clock High Trip Level VDCON _ = 1.25V to VVL 1.00 1.05 1.10 V
Maximum Duty Cycle
Adjustment Range4090 %
Maximum Duty CycleVDCON _ = 0.625V43%
Default Maximum Duty CycleVDCON _ = 1.25V to VVL76%DCON_ Input Leakage Current VDCON _ = 0V to 3V 0.01 1 µADCON_ Input Sleep-Mode
Threshold VDCON _ rising, 50mV hysteresis 0.35 0.4 0.45 V
AUXILIARY ERROR AMPLIFIER FB_ Regulation Voltage Unity gain configuration, FB_ = COMP_ 1.233 1.248 1.263 VFB_ to COMP_
Transconductance GEA Unity gain configuration, FB_ = COMP_, -5µA < ILOAD < 5µA 70 100 160 µsFB_ Input Leakage Current VFB_ = 1.35V 5 100 nA
AUXILIARY DRIVERS (DL1, DL2, DL3) DL_ Driver Resistance Output high or low 4 11 ΩDL_ Drive Current Sourcing or sinking, VDL_ = VVDDC / 2 400 mA
AUXILIARY SOFT-START Soft-Start Interval1024OSC
cycles
AUXILIARY SHORT-CIRCUIT PROTECTIONFault Interval1024OSC
cycles
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)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSGENERAL Input Voltage Range VIN 2.5 11 V
SUPPLY CURRENT Shutdown Supply Current (from VDDM and VDDC) VONM = 0 20 µAVFBM = 1.5V, VVDDC = 0 600 Main DC-DC Converter Supply Current (from VDDM) VFBM = 1.5V, VVDDC = 3V 55 µAMain DC-DC Converter Supply Current (from VDDC) VFBM = 1.5V, VVDDC = 3V 450 µAMain plus Core Supply Current (from VDDC) VFBM = VFBC = 1.5V, VONC = 3V 700 µAMain plus Auxiliary 1 Supply
Current (from VDDC) VFBM = VFB1 = 1.5V, VON1 = VDCON1 = 3V 750 µAMain plus Auxiliary 2 Supply
Current (from VDDC) VFBM = VFB2 = 1.5V, VDCON2 = 3V 750 µAMain plus Auxiliary 3 Supply
Current (from VDDC) VFBM = VFB3 = 1.5V, VDCON3 = 3V 750 µATotal Supply Current (from VDDC) VFBM = VFBC = VFB1 = VFB2 = VFB3 = 1.5V,
VONC = VON1 = VDCON1 = VDCON2 =
VDCON3 = 3V 1700 µA
VL REGULATOR VL Output Voltage 6V < VVDDM < 11V, 0.1mA < ILOAD < 10mA 2.83 3.12 VVL Supply Rejection 3.5V < VVDDM < 11V, VVDDC = 0 3 %VL Undervoltage Lockout
Threshold VL rising, 40mV hysteresis 2.25 2.50 VVL Switchover Voltage to VDDC VL rising, 100mV hysteresis 2.3 2.5 VVL to VDDC Switch Resistance 7 Ω
REFERENCE Reference Output Voltage VREF IREF = 20µA 1.230 1.262 VREF Load Regulation 10µA < IREF < 200µA 9 mVREF Line Rejection 2.7V < VOUT < 5.5V 5 mVREF Undervoltage Lockout
Threshold REF rising, 20mV hysteresis 0.9 1.1 V
OSCILLATOR OSC Discharge Trip Level OSC rising 1.225 1.275 VOSC Input Bias Current VOSC = 1.1V 100 nAOSC Discharge Resistance VOSC = 1.5V 100 Ω
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)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSLOGIC INPUTS (ONM, ONC, ON1) Input Low Level VIL 0.4 VONM 1.8 Input High Level VIH ONC, ON1 1.6 VInput Leakage Current ONM: VIN = 0 or 11V; ONC, ON1: VIN = 0 or 5V 1 μA
MAIN DC-DC CONVERTER Main Output Voltage Adjust Range VOUT 2.7 5.5 VMain Idle Mode Threshold VOSC = 0.625V, measured between
VDDM and LXM 2 35 mVMain Current-Sense Amplifier Voltage Gain AVCSM Measured between VDDM and LXM 8.4 10.2 V/VMain Zero-Crossing Threshold Measured between LXM and PGNDM -20 -8 mVMain Slope Compensation Gain AVSWM 0.16 0.24 V/V
MAIN ERROR AMPLIFIER FBM Regulation Voltage Unity gain configuration, FBM = COMPM 1.230 1.265 VFBM to COMPM
Transconductance GEA U ni ty g ai n confi g ur ati on, FBM = C OM P M ,5μA < ILOA D < 5μA 70 160 μSFBM Input Leakage Current VFBM = 1.35V 100 nACOMPM Minimum Output
Voltage VFBM = 1.35V, COMPM open 0.3 VCOMPM Maximum Output Voltage VCOMPM(MAX) VFBM = 1.15V, COMPM open 2.00 2.27 V
MAIN DRIVERS (DHM, DLM) Output Low Voltage ISINK = 10mA 0.11 VOutput High Voltage ISOURCE = 10mA VVDDM -
0.11 VDriver Resistance IDHM = 10mA, IDLM = 10mA 11 Ω
CORE DC-DC CONVERTER (VONC = 3V) Core Output Voltage Adjust
Range VOUT 1.25 5.5 VCore Idle Mode Threshold VOSC = 0.625V 40 360 mACore Current-Sense Amplifier Transresistance RCSC 0.7 1.3 V/ACore Slope Compensation Gain AVSWC 0.16 0.24 V/V
CORE ERROR AMPLIFIER (VONC = 3V) FBC Regulation Voltage Unity gain configuration, FBC = COMPC 1.230 1.265 VFBC to COMPC
Transconductance GEA U ni ty g ai n confi g ur ati on, FBC = C OM P C ,5μA < ILOA D < 5μA 70 160 μS
MAX1802
Digital Camera Step-Down
Power Supply PARAMETER
SYMBOL CONDITIONS MIN TYP MAX UNITSFBC Input Leakage Current VFBC = 1.35V 100 nACOMPC Minimum Output
Voltage VFBC = 1.35V, COMPC open 0.3 VCOMPC Maximum Output
Voltage VCOMPC(MAX) VFBC = 1.15V, COMPC open 2.00 2.27 V
CORE POWER SWITCHES (VONC = 3V) LXC Leakage Current VLXC = 0, 5.5V 20 µARDSN N-channel, ILXC = 0.75A 350 Switch On-Resistance RDSP P-channel, ILXC = 0.75A 400 mΩN-Channel Turn-Off Current 5 190 mA
AUXILIARY DC-DC CONTROLLERS 1, 2, 3 (VON1 = VDCON_= 3V) INTERNAL CLOCK OSC Clock Low Trip Level OSC falling edge 0.2 0.3 VVDCON_ = 0.625V 0.575 0.675 V OSC Clock High Trip Level VDCON_ = 1.25V to VVL 1.00 1.10
Maximum Duty Cycle
Adjustment Range4090 %DCON_ Input Leakage Current VDCON_ = 0V to 3V 1 µADCON_ Input Sleep-Mode
Threshold VDCON_ rising, 50mV hysteresis 0.35 0.45 V
AUXILIARY ERROR AMPLIFIER FB_ Regulation Voltage Unity gain configuration, FB_ = COMP_ 1.230 1.265 VFB_ to COMP_
Transconductance GEA Unity gain configuration, FB_ = COMP_,
-5µA < ILOAD < 5µA 70 160 µsFB_ Input Leakage Current VFB_ = 1.35V 100 nA
AUXILIARY DRIVERS (DL1, DL2, DL3) DL_ Driver Resistance Output high or low 11 Ω
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)
Note 1:Specifications to -40°C are guaranteed by design and not production tested.
MAX1802
Digital Camera Step-Down
Power SupplyEFFICIENCY vs. LOAD CURRENT
(CORE CONVERTER)
MAX1802 toc03
LOAD CURRENT (mA)
EFFICIENCY (%)40
VIN = +2.5V
VIN = +5V
VIN = +3.3V
VOUT = +1.8V
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.)
10010100100010,000
EFFICIENCY vs. LOAD CURRENT
(MAIN CONVERTER)MAX1802 toc01
LOAD CURRENT (mA)
EFFICIENCY (%)40
VOUT = 3.3V
VIN = +5V
VIN = +7.2V
VIN = +11V
10010100100010,000
EFFICIENCY vs. LOAD CURRENT
(MAIN CONVERTER)MAX1802 toc02
LOAD CURRENT (mA)
EFFICIENCY (%)40
VOUT = +5V
VIN = +7.2V
VIN = +11V
EFFICIENCY vs. LOAD CURRENT
(CORE CONVERTER)
MAX1802 toc04
LOAD CURRENT (mA)
EFFICIENCY (%)40
VIN = +5V
VIN = +3.3V
VOUT = +2.5V
MAXIMUM DUTY CYCLE vs. VDCON_
MAX1802 toc05
VDCON_ (V)
MAXIMUM DUTY CYCLE (%)
DEFAULT MAXIMUM DUTY CYCLE
vs. FREQUENCY
MAX1802 toc06
FREQUENCY (kHz)
DEFAULT MAXIMUM DUTY CYCLE (%)
COSC = 470pF
OSCILLATOR FREQUENCY
vs. ROSC
MAX1802 toc07
ROSC (kΩ)
OSCILLATOR FREQUENCY (kHz)
800COSC = 470pF
COSC = 220pF
COSC = 100pF
COSC = 47pF2681012
MAX1802 toc08
INPUT VOLTAGE (V)
SHUTDOWN CURRENT (
SHUTDOWN CURRENT
vs. INPUT VOLTAGE
MAX1802 toc10
REFERENCE CURRENT (μA)
REFERENCE VOLTAGE (V)
REFERENCE VOLTAGE
vs. REFERENCE CURRENT110010100010,000
MAX1802 toc11
FREQUENCY (kHz)
SMALL-SIGNAL RESPONSE (dB)
FB_ TO COMP_ SMALL-SIGNAL
OPEN-LOOP FREQUENCY RESPONSE
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.)
1ms/div
MAIN OUTPUT STARTUP RESPONSEMAX1802 toc12
VONM
5V/div
VMAIN
2V/div
IOUT
200mA/div
1ms/div
CORE OUTPUT STARTUP RESPONSEMAX1802 toc13
VONC
5V/div
VCORE
2V/div
IOUT
100mA/div
1ms/div
AUXILIARY CONTROLLER
STARTUP RESPONSEMAX1802 toc14
VON_
5V/div
VOUT
2V/div
IOUT
200mA/div
MAX1802 toc09
TEMPERATURE (°C)
REFERENCE VOLTAGE (V)
REFERENCE VOLTAGE
vs. TEMPERATURE
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.)
1ms/div
STARTUP SEQUENCEMAX1802 toc15
VONM
5V/div
VMAIN
2V/div
VCORE
2V/div
400μs/div
MAIN OUTPUT
LOAD-TRANSIENT RESPONSEMAX1802 toc16
VOUT
AC-COUPLED
100mV/div
ILOAD
200mA/div
COUT = 100μF
500μs/div
CORE OUTPUT
LOAD-TRANSIENT RESPONSEMAX1802 toc17
VOUT
AC-COUPLED
200mV/div
ILOAD
100mA/div
VOUT = 2.5V
400μs/div
AUXILIARY OUTPUT
LOAD-TRANSIENT RESPONSEMAX1802 toc18
VOUT
AC-COUPLED
100mV/div
ILOAD
200mA/div
2.5ms/div
MAIN TRANSIENT RESPONSE
SUBJECT TO CORE TRANSIENTMAX1802 toc19
VOUT (MAIN)
AC-COUPLED
20mV/div
ILOAD (CORE)
100mA/div0A
VOUT = 2.5V
MAX1802
Digital Camera Step-Down
Power Supply
Pin DescriptionPIN NAME FUNCTION1 FBM Main DC-DC Converter Feedback Input. Connect a feedback resistive voltage-divider from the output
to FBM to set the main output voltage. Regulation voltage is VREF (1.25V).2 COMPM Compensation for Main Controller. Output of main transconductance error amplifier. Connect a series
resistor and capacitor to GND to compensate the main control loop (see Compensation Design).3 ONM Main Converter Enable Input. High level turns on the main converter and VL regulator. Connect ONM
to VDDM to automatically start the converter. When the main converter is off, all other outputs are
disabled.4 VH Internal Bias Voltage. VH provides bias to the main controller. Bypass VH to VDDM with a 0.1µF or
greater ceramic capacitor.5 VDDM Battery Input. VDDM supplies power to the IC and also serves as a high-side current-sense input
for the main DC-DC controller. Connect VDDM as close as possible to the source of the external
P-channel switching MOSFET for the main controller.6 DHM External P-Channel MOSFET Gate-Drive Output for Main Controller. DHM swings between VDDM and
PGNDM with 400mA (typ) drive current. Connect DHM to the gate of the external P-channel switching
MOSFET for the main controller.7 LXM Main DC-DC Controller Current-Sense Input. Connect LXM to the drains of the external P- and N-
channel switching MOSFETs for the main converter. LXM serves as the current-sense input for both P- and N-channel switching MOSFETs. Connect LXM as close as possible to the drain of the external
P-channel switching MOSFET for the main controller.8 DLM External N-Channel MOSFET Gate-Drive Output for Main Controller. DLM swings between VDDM
and PGNDM with 400mA (typ) drive current. Connect DLM to the gate of the external N-channel
switching MOSFET for the main controller.9 PGNDMP ow er G r ound for M ai n D C - D C C ontr ol l er . P G N D M al so ser ves as a l ow - si d e cur r ent- sense i np ut for
the m ai n D C - D C contr ol l er . C onnect P GN D M as cl ose as p ossi b l e to the sour ce of the exter nal - channel sw i tchi ng M OS FE T for the m ai n contr ol l er .10 OSC Oscillator Control. Connect a timing capacitor from OSC to GND and a timing resistor from OSC to VL
to set the switching frequency between 100kHz and 1MHz (see Setting the Switching Frequency).11 DCON1 Maximum Duty Cycle Control Input for Auxiliary Controller 1. Connect DCON1 to VL to set the default
maximum duty cycle. Connect a resistive voltage-divider from REF to DCON1 to set the maximum
duty cycle between 40% and 90%. Pull DCON1 below 300mV to turn the controller off.12 DL1 External MOSFET Gate Drive Output for Auxiliary Controller 1. DL1 swings between VDDC and PGND
with 400mA (typ) drive current. Connect DL1 to the gate of the external switching N-channel MOSFET
for auxiliary controller 1.13 ON1 Enable Input for Auxiliary Controller 1. Connect ON1 to VL to automatically start auxiliary controller 1.14 COMP1Compensation for Auxiliary Controller 1. Output of auxiliary controller 1 transconductance error
amplifier. Connect a series resistor and capacitor from COMP1 to GND to compensate the auxiliary
controller 1 control loop (see Compensation Design).15 FB1 Feedback Input for Auxiliary Controller 1. Connect a feedback resistive voltage-divider from the
output of auxiliary controller 1 to FB1 to set the output voltage. Regulation voltage is VREF (1.25V).16 FB2 Feedback Input for Auxiliary Controller 2. Connect a feedback resistive voltage-divider from the
output of auxiliary controller 2 to FB2 to set the output voltage. Regulation voltage is VREF (1.25V).
MAX1802
Digital Camera Step-Down
Power SupplyPIN NAME FUNCTION17 COMP2Compensation for Auxiliary Controller 2. Output of auxiliary controller 2 transconductance error
amplifier. Connect a series resistor and capacitor from COMP2 to GND to compensate the auxiliary
controller 2 control loop (see Compensation Design).18 DCON2Maximum Duty Cycle Control Input for Auxiliary Controller 2. Connect DCON2 to VL to set the default
maximum duty cycle. Connect a resistive voltage-divider from REF to DCON2 to set the maximum
duty cycle between 40% and 90%. Pull DCON2 below 300mV to turn the controller off.19 DL2External MOSFET Gate Drive Output for Auxiliary Controller 2. DL2 swings between VDDC and PGND
with 400mA (typ) drive current. Connect DL2 to the gate of the external switching N-channel MOSFET
for auxiliary controller 2.20 DL3External MOSFET Gate Drive Output for Auxiliary Controller 3. DL3 swings between VDDC and PGND
with 400mA (typ) drive current. Connect DL3 to the gate of the external switching N-channel MOSFET
for auxiliary controller 3.21 COMP3Compensation for Auxiliary Controller 3. Output of auxiliary controller 3 transconductance error
amplifier. Connect a series resistor and capacitor from COMP3 to GND to compensate the auxiliary
controller 3 control loop (see Compensation Design).22 FB3 Feedback Input for Auxiliary Controller 3. Connect a feedback resistive voltage-divider from the
output of auxiliary controller 3 to FB3 to set the output voltage. Regulation voltage is VREF (1.25V).23 DCON3Maximum Duty Cycle Control Input for Auxiliary Controller 3. Connect DCON3 to VL to set the default
maximum duty cycle. Connect a resistive voltage-divider from REF to DCON3 to set the maximum
duty cycle between 40% and 90%. Pull DCON3 below 300mV to turn the controller off.24 ONC Core Converter Enable Input. High level turns on the core converter. Connect ONC to VL to
automatically start the core converter.25 PGND Power Ground. Sources of internal N-channel MOSFET power switches. Connect PGND to GND as
close to the IC as possible.26 LXC Core Power Switching Node. Drains of the internal P- and N-channel MOSFET switches for the core
converter.27 VDDCCore DC-DC Converter Power Input. VDDC is connected to the source of the internal P-channel
MOSFET power switch for the core converter. VDDC is limited to 5.5V. For battery voltages greater than 5.5V, connect VDDC to the main output. Bypass VDDC to PGND with a 1μF or greater ceramic
capacitor.28 VLInternal Low-Voltage Bypass. The internal circuitry is powered from VL. An internal linear regulator
powers VL from VDDM when VDDC is less than 2.4V. When VDDC is greater than 2.4V, an internal
switch connects VL to VDDC. Bypass VL to GND with a 1.0μF or greater ceramic capacitor.29 COMPC Compensation for Core Converter. Output of core transconductance error amplifier. Connect a series
resistor and capacitor to GND to compensate the core control loop (see Compensation Design).30 FBC Core DC-DC Converter Feedback Input. Connect a feedback resistive voltage-divider from the core
output to FBC to set the output voltage. Regulation voltage is VREF (1.25V).31 REF 1.25V Reference Output. Bypass REF to GND with a 0.1μF or greater ceramic capacitor.32 GND Analog Ground
Pin Description (continued)
MAX1802
Digital Camera Step-Down
Power Supply
Detailed DescriptionThe 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 ConfigurationThe 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 ConverterThe 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.VAV
LIM
COMPMMAXREFOUTVSWM
VCSMDSP
OUTMAXLIM
OUT
OUT
OSC
