MAX8595XETA ,High-Efficiency, 36V Step-Up Converters with TA Derating Option for 2 to 9 White LEDsELECTRICAL CHARACTERISTICS(V = 3.0V, L = 22µH, C = 2.2µF, C = 0.1µF, C = 0.1µF, R = 13Ω , V = 1.5V, ..
MAX8595XETA ,High-Efficiency, 36V Step-Up Converters with TA Derating Option for 2 to 9 White LEDsApplications♦ Pin Compatible with the MAX1561 and MAX1599Cell Phones and Smart Phones♦ TDFN 3mm x 3 ..
MAX8595XETA+ ,High-Efficiency, 36V Step-Up Converters with TA Derating Option for 2 to 9 White LEDsELECTRICAL CHARACTERISTICS(V = 3.0V, L = 22µH, C = 2.2µF, C = 0.1µF, C = 0.1µF, R = 13Ω , V = 1.5V, ..
MAX8595XETA+T ,High-Efficiency, 36V Step-Up Converters with TA Derating Option for 2 to 9 White LEDsFeatures♦ Up to Nine LEDs at 25mAThe MAX8595X/MAX8596X drive up to nine white LEDswith constant cur ..
MAX8595ZETA+ ,High-Efficiency, 32V Step-Up Converters with TA Derating Option for 2 to 8 White LEDsApplications ♦ TDFN 3mm x 3mm x 0.8mm Package with Exposed PaddleCell Phones and Smart PhonesOrderi ..
MAX8595ZETA+T ,High-Efficiency, 32V Step-Up Converters with TA Derating Option for 2 to 8 White LEDsfeatures an♦ Flexible Dimming Controlambient-temperature derating function to avoid over-Analogdriv ..
MB84256A-10LLP , CMOS 256K-BIT LOW POWER SRAM
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MAX8595XETA
High-Efficiency, 36V Step-Up Converters with TA Derating Option for 2 to 9 White LEDs
General DescriptionThe MAX8595X/MAX8596X drive up to nine white LEDs
with constant current and high efficiency to provide
LCD backlighting in cell phones, PDAs, and other
handheld devices. The series connection allows the
LED currents to be identical for uniform brightness and
minimizes the number of traces to the LEDs. The
MAX8595X regulates constant LED current over the
entire temperature range. The MAX8596X features an
ambient-temperature derating function to avoid over-
driving the white LEDs during high ambient tempera-
tures, enabling higher drive current below +42°C.
A single Dual Mode™ input provides a simple means of
brightness adjustment and on/off control. Fast 1MHz
current-mode PWM operation allows for small input and
output capacitors and a small inductor while minimizing
ripple on the input supply/battery. Soft-start eliminates
inrush current during startup.
The MAX8595X/MAX8596X are available in a space-
saving, 8-pin, 3mm x 3mm TDFN package.
ApplicationsCell Phones and Smart Phones
PDAs, Palmtops, and Wireless Handhelds
e-Books and Subnotebooks
White LED Display Backlighting
FeaturesUp to Nine LEDs at 25mATemperature Derating Function to Allow Fewer
LEDs for Same Light (MAX8596X)86% Efficiency (PLEDs / PIN)1.7% Current-Regulation AccuracyOutput Overvoltage ProtectionFlexible Dimming Control
Analog
Direct-PWM Internal Filter1MHz PWM Switching Frequency0.1µF Output Capacitor12mVP-PLow Input Ripple Soft-Start Eliminates Inrush Current2.6V to 5.5V Input Range0.3µA Shutdown CurrentPin Compatible with the MAX1561 and MAX1599TDFN 3mm x 3mm x 0.8mm Package with
Exposed Paddle
MAX8595X/MAX8596X, 36V Step-Up Converters
with TADerating Option for 2 to 9 White LEDs
Pin Configuration
Ordering Information
Typical Operating CircuitDual Mode is a trademark of Maxim Integrated Products, Inc.*Future product—contact factory for availability.
MAX8595X/MAX8596X
High-Efficiency, 36V Step-Up Converters
with TADerating Option for 2 to 9 White LEDs
ABSOLUTE MAXIMUM RATINGSStresses 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 to GND.................................................................-0.3V to +6V
PGND to GND.......................................................-0.3V to +0.3V
LX, OUT to GND.....................................................-0.3V to +40V
CTRL to GND...................-0.3V to the lower of +6V or (VIN+ 2V)
COMP, CS to GND......................................-0.3V to (VIN+ 0.3V)
ILX...................................................................................1.0ARMS
Continuous Power Dissipation (TA= +70°C)
8-Pin TDFN 3mm x 3mm
(derate 24.4mW/°C above +70°C)............................1950mW
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
ELECTRICAL CHARACTERISTICS(VIN= 3.0V, L = 22µH, CIN= 2.2µF, COUT= 0.1µF, CCOMP= 0.1µF, RSENSE= 13Ω, VCTRL= 1.5V, TA= -40°C to +85°C, unless other-
MAX8595X/MAX8596X
High-Efficiency, 36V Step-Up Converters
with TADerating Option for 2 to 9 White LEDs
ELECTRICAL CHARACTERISTICS (continued)(VIN= 3.0V, L = 22µH, CIN= 2.2µF, COUT= 0.1µF, CCOMP= 0.1µF, RSENSE= 13Ω, VCTRL= 1.5V, TA= -40°C to +85°C, unless other-
wise noted. Typical values are at TA= +25°C.) (Note 1)
Note 1:Parameters are 100% production tested at TA= +25°C. Limits over the operating temperature range are regulated by
design and characterization.
Note 2:VDis the forward-voltage drop of the Schottky diode in Figure 1.
Note 3:Time from CTRL going below the Dual-Mode threshold to IC shutdown.
MAX8595X/MAX8596X
High-Efficiency, 36V Step-Up Converters
with TADerating Option for 2 to 9 White LEDs
Typical Operating Characteristics(Circuit of Figure 1, VIN= 3.6V, ILED= 25mA, L = 22µH, CIN= 2.2µF, COUT= 0.1µF, CCOMP= 0.1µF, RSENSE= 13Ω, 4 LEDs, TA= +25°C,
unless otherwise noted.)
MAX8595X/MAX8596X
High-Efficiency, 36V Step-Up Converters
with TADerating Option for 2 to 9 White LEDsypical Operating Characteristics (continued)(Circuit of Figure 1, VIN= 3.6V, ILED= 25mA, L = 22µH, CIN= 2.2µF, COUT= 0.1µF, CCOMP= 0.1µF, RSENSE= 13Ω, 4 LEDs, TA= +25°C,
unless otherwise noted.)
DIRECT-PWM DIMMING RESPONSEMAX8595X toc08
10µs/div
VCTRL2V/div
32kHz 50%
DUTY CYCLE
500mV/div
AC-COUPLED
10mA/div
20mV/div
AC-COUPLEDVIN
VOUT
ILED
CTRL STEP RESPONSEMAX8595X toc07
20ms/div
VCTRL1V/div
40mA/div
10V/div
100mA/divIIN
ILED
VOUT
MAX8595X/MAX8596X
Detailed DescriptionThe high efficiency and small size of the MAX8595X/
MAX8596X make them ideally suited to drive up to nine
series-connected LEDs. These devices operate as a
boost DC-DC converter that regulates output current
rather than voltage. The MAX8595X/MAX8596X provide
even illumination by sourcing the same output current
through each LED, eliminating the need for expensive
factory calibration. The fast 1MHz internal oscillator
allows for a small inductor and small input and output
capacitors while minimizing input and output ripple.
The single analog control input (CTRL) allows easy
adjustment of LED brightness and on/off control. This
allows simple logic-level on/off control, analog voltage
control, or PWM duty-cycle control of both brightness
and shutdown. In shutdown, supply current is reduced
to a low 0.3µA (typ). A soft-start gradually illuminates
the LEDs, eliminating the inrush current during startup.
The MAX8596X has the additional feature of derating
LED current as ambient temperature rises. Above
+42°C, the CS regulation voltage is reduced at a rate of
5.5mV/°C, thus reducing the LED current.
Soft-StartThe MAX8595X/MAX8596X attain soft-start by charging
CCOMPgradually with a current source. When VCOMP
rises above 1.25V, the internal MOSFET begins switch-
ing at a reduced duty cycle. When VCOMPrises above
2.25V, the duty cycle is at its maximum. See the
Typical Operating Characteristics for an example of
soft-start operation.
ShutdownThe MAX8595X/MAX8596X enter shutdown when VCTRL
is less than 100mV for more than 8.2ms. In shutdown,
supply current is reduced to 0.3µA (typ) by powering
down the entire IC except for the CTRL voltage-detec-
tion circuitry. CCOMPis discharged during shutdown,
allowing the device to reinitiate soft-start when it is
enabled. Although the internal n-channel MOSFET does
not switch in shutdown, there is still a DC current path
between the input and the LEDs through the inductor
and Schottky diode. The minimum forward voltage of the
LED array must exceed the maximum input voltage to
ensure that the LEDs remain off in shutdown. However,
with two or more LEDs, the forward voltage is large
enough to keep leakage current low, less than 1µA
(typ). Typical shutdown timing characteristics are shown
in the Typical Operating Characteristics.
Overvoltage ProtectionOvervoltage lockout (OVLO) occurs when VOUTis
above 38V (typ). The protection circuitry stops the inter-
nal MOSFET from switching and causes VCOMPto
decay towards 0V. The device comes out of OVLO and
into soft-start when VOUTfalls below 36V (typ).
Ambient Temperature Derating Function
(MAX8596X)The MAX8596X limits the maximum LED current
depending on the die temperature. VCSis limited to
343mV up to +42°C. Once the temperature reaches
+42°C, the maximum VCS declines by 5.5mV/°C until
the minimum 106.5mV threshold is reached at +85°C.
Due to the package’s exposed paddle, the die temper-
ature is always very close to the PC board temperature.
The temperature derating function allows the LED cur-
rent to be safely set higher at normal operating temper-
atures, thereby allowing either a brighter display or
fewer LEDs to be used for normal display brightness.
See the Typical Operating Characteristicsfor LED
Current vs. Ambient Temperature.
High-Efficiency, 36V Step-Up Converters
with TADerating Option for 2 to 9 White LEDs
