MAX8645YETI+ Maxim Integrated Products, MAX8645YETI+ Datasheet - Page 9

• Manufacturer Part Number: MAX8645YETI+
• Description: IC LED DRVR WHITE BCKLGT 28-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Backlight, White LEDr

Specifications of MAX8645YETI+

• Constant Current: Yes
• Topology: Linear (LDO), Switched Capacitor (Charge Pump)
• Number Of Outputs: 8
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 1MHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Voltage - Output: 5.5V
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 200mA
• Internal Switch(s): Yes
• Efficiency: 85%
• Number Of Segments: 8
• Low Level Output Current: 400000 uA (Typ)
• Operating Supply Voltage: 2.7 V to 5.5 V
• Maximum Supply Current: 5.5 mA
• Maximum Power Dissipation: 1666 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Led Driver Application: Backlighting And Flash, Digital Cameras And Camcorders
• No. Of Outputs: 8
• Output Current: 200mA
• Output Voltage: 5.5V
• Input Voltage: 2.7V To 5.5V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX8645X/MAX8645Y charge pumps drive up to
six white LEDs in the main display for backlighting and
up to two white LEDs for flash, all with regulated con-
stant current for uniform intensity. By utilizing adaptive
1x/1.5x/2x charge-pump modes and very-low-dropout
current regulators, they achieve high efficiency over the
1-cell lithium-battery input voltage range. 1MHz fixed-
frequency switching allows for tiny external compo-
nents and low input ripple. Two on-board 200mA
programmable-output-voltage LDOs are provided to
meet camera-module requirements.
When V
MAX8645Y operate in 1x mode and V
to V
current. As V
below the switchover threshold of 100mV and the
MAX8645X/MAX8645Y start switching in 1.5x mode.
When the input voltage rises above V
mately 50mV, the MAX8645X/MAX8645Y switch back to
1x mode.
When V
the MAX8645X/MAX8645Y operate in 1.5x mode. The
internal current regulators regulate the LED current. As
V
switchover threshold of 100mV, and the MAX8645X/
MAX8645Y start switching in 2x mode. When the input
voltage rises above 2/3 V
the MAX8645X/MAX8645Y switch back to 1.5x mode.
True Shutdown is a trademark of Maxim Integrated Products, Inc.
IN
IN
1x/1.5x/2x White LED Charge Pumps with Two
drops, V
PIN
23
24
25
26
27
28
—
. The internal current regulators regulate the LED
IN
IN
is less than V
is higher than V
M_
IN
NAME
PGND
drops, V
OUT
C2N
C1P
C2P
(or V
_______________________________________________________________________________________
P1
EP
Detailed Description
F_
OUT
) eventually falls below the
OUT
M_
Transfer Capacitor 1 Positive Connection. Connect a 1µF ceramic capacitor between C1P and C1N.
During shutdown, if OUT > IN, C1P is shorted to OUT. If OUT < IN, C1P is shorted to IN.
Power Ground. Connect PGND to system ground. PGND is used for charge-pump switching currents.
Charge-Pump Output. Bypass OUT to GND with a 10µF ceramic capacitor. Connect to the anodes of
all the LEDs. OUT is internally pulled to ground through a 5kΩ resistor during shutdown.
Transfer Capacitor 2 Positive Connection. Connect a 1µF ceramic capacitor between C2P and C2N.
During shutdown, if OUT > IN, C2P is shorted to OUT. If OUT < IN, C2P is shorted to IN.
Transfer Capacitor 2 Negative Connection. Connect a 1µF ceramic capacitor between C2P and C2N.
C2N is internally shorted to IN during shutdown.
Default Output-Voltage Select Input. P1 and P2 set the LDO1 and LDO2 voltages to one of nine
combinations (Table 2). P1 is high impedance in an off condition and shortly after in an on condition.
Exposed Paddle. Connect to GND and PGND.
1x to 1.5x Switchover
1.5x to 2x Switchover
but greater than 2/3 V
(or V
by approximately 50mV,
OUT
F_
, the MAX8645X/
) eventually falls
OUT
OUT
is pulled up
by approxi-
OUT
LDOs in 4mm x 4mm TQFN
,
The MAX8645X/MAX8645Y include soft-start circuitry to
limit inrush current at turn-on. Once the input voltage is
applied, the output capacitor is charged directly from
the input with a ramped current source (with no charge-
pump action) until the output voltage approaches the
input voltage. Once the output capacitor is charged,
the charge pump determines if 1x, 1.5x, or 2x mode is
required. In the case of 1x mode, the soft-start is termi-
nated and normal operation begins. In the case of 1.5x
or 2x mode, soft-start operates until the lowest voltage
of M1–M6 and F1, F2 reaches regulation. If the output
is shorted to ground or is pulled to less than 1.25V, the
output current is limited by soft-start.
When ENM1, ENM2, and ENF are simultaneously held
low for 2.5ms or longer, the MAX8645X/MAX8645Y are
shut down and put in a low-current shutdown mode,
and the input is isolated from the output. OUT is inter-
nally pulled to GND with 5kΩ during shutdown.
The MAX8645X/MAX8645Y limit the maximum LED cur-
rent depending on the die temperature. The maximum
LED current is set by the R
Once the temperature reaches +40°C, the LED current
decreases by 1.7%/°C. Due to the package’s exposed
paddle, the die temperature is always very close to the
PCB 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.
FUNCTION
Pin Description (continued)
True Shutdown™ Mode
SETM
Thermal Derating
and R
SETF
Soft-Start
resistors.
9