MAX6620_14 Datasheet, PDF (7/30 Pages) Maxim Integrated Products – Quad Linear Fan-Speed Controller

MAX6620
Quad Linear Fan-Speed Controller
Pin Description
PIN
NAME
FUNCTION
1
SCL
I²C Serial-Clock Input. Can be pulled up to 5.5V regardless of V_CC. Open circuit when V_CC = 0V.
2
SDA
Open-Drain, I²C Serial-Data Input/Output. Can be pulled up to 5.5V regardless of V_CC. Open
circuit when V_CC = 0V.
Startup Watchdog Set Input. This input is sampled when power is first applied and sets the initial
I²C watchdog behavior. When connected to GND, the watchdog function is disabled. When
3
WD_START _{connected to VCC, the MAX6620 monitors SDA. If 10s elapse without a valid I2C transaction, the}
fan drive goes to 100%.
4, 10, 11, 18,
25
5
6
GND
Ground
ADDR
DAC_START
I²C Address Set Input. This input is sampled when power is first applied and sets the I²C slave
address. When connected to GND, the slave address will be 0x50. When unconnected, the slave
address will be 0x52. When connected to V_CC, the slave address will be 0x54.
Startup Fan Drive DAC Set Input. This input is sampled when power is first applied and sets the
power-up value for the fan drive voltage. When connected to GND, the fan drive voltage will be
0%. When unconnected, the fan drive voltage will be 75%. When connected to V_CC, the fan drive
voltage will be 100%.
Startup Spin-Up Set Input. This input is sampled when power is first applied and sets the initial
spin-up behavior. When connected to GND, spin-up is disabled. When connected to V_CC at
7
SPINUP_START
power-up, the fan is driven with a full-scale drive voltage until two tachometer pulses have been
detected, or 1s has elapsed. When unconnected, the fan is driven with a full-scale drive voltage
until two tachometer pulses have been detected, or 0.5s has elapsed. Spin-up behavior may be
modified by writing appropriate settings to the MAX6620’s registers.
Crystal Oscillator Inputs. Connections for a standard 32.768kHz quartz crystal. The internal
oscillator circuitry is designed for operation with a crystal having a specified load capacitance
8, 9
X1, X2
(C_L) of 12pF. Connect an external 32.768kHz oscillator across X1 and X2 for operation with the
external oscillator. If no crystal or external oscillator is connected, the MAX6620 will use its
internal oscillator.
12, 17, 19, 24
DACOUT4– Fan Drive DAC Outputs. Connect to the gate of a p-channel MOSFET or base of a PNP bipolar
DACOUT1 transistor.
13, 16, 20, 23
DACFB4–
DACFB1
DAC Feedback Inputs. Connect a 0.1µF capacitor between these pins and GND. Connect to the
supply pin of the fan and to the drain of a p-channel MOSFET or collector of a PNP bipolar transistor.
14, 15, 21, 22
26
TACH4–TACH1 Fan Tachometer Logic Inputs. These inputs accept input voltages up to V_FAN.
FAN
Fan Power-Supply Voltage Input. Connect to the fan power supply (V_FAN). Bypass with a 0.1µF
capacitor to GND.
27
VCC
Power-Supply Input. 3.3V nominal. Bypass V_CC to GND with a 0.1µF capacitor.
28
FAN_FAIL
Active-Low, Open-Drain Fan Failure Output. Active only when fault is present; open-circuit when
V_CC = 0V. This pin can be pulled up to 5.5V regardless of V_CC.
—
EP
Exposed Paddle. Internally connected to GND. Connect to a large ground plane to maximize
thermal performance. Not intended as an electrical connection point.
Maxim Integrated
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