PM6685 STMicroelectronics, PM6685 Datasheet - Page 30

• Manufacturer Part Number: PM6685
• Description: IC CTLR DUAL SYNC STDN 5X5VFQFPN
• Manufacturer: STMicroelectronics

Specifications of PM6685

• Applications: Controller, Notebook Power System
• Voltage - Input: 6 ~ 28 V
• Number Of Outputs: 2
• Voltage - Output: -3.3V, 5V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN, 32-VFQFPN
• Output Voltage: 5 V, 3.3 V
• Output Current: 0.1 A
• Input Voltage: 5.5 V to 28 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 10 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Monitoring and protections
8.5
8.6
8.7
30/48
Table 10.
Design guidelines
The design of a switching section starts from two parameters:
●
●
Switching frequency
It’s possible to set 3 different working frequency ranges for the two sections: 200 kHz/300
kHz, 400 kHz/500 kHz, 600 kHz/700 kHz with FSEL pin.
Switching frequency mainly influences two parameters:
●
●
Inductor selection
Once that switching frequency is defined, inductor selection depends on the desired
inductor ripple current and load transient performance.
Low inductance means great ripple current and could generate great output noise. On the
other hand, low inductor values involve fast load transient response.
A good compromise between the transient response time, the efficiency, the cost and the
size is to choose the inductor value in order to maintain the inductor ripple current ΔIL
between 20% and 50% of the maximum output current ILOAD(max). The maximum ΔIL
occurs at the maximum input voltage. With this considerations, the inductor value can be
calculated with the following relationship:
Equation 10
Undervoltage
Overvoltage
protection
protection
shutdown
Thermal
Mode
Input voltage range: in notebook applications it varies from the minimum battery
voltage, VINmin to the AC adapter voltage, VINmax.
Maximum load current: it is the maximum required output current, ILOAD(max).
Inductor size: for a given saturation current and RMS current, greater frequency allows
to use lower inductor values, which means smaller size.
Efficiency: switching losses are proportional to frequency. High frequency generally
involves low efficiency.
Protections and operatives modes
OUT5/OUT3 > 115% of the
nominal value
OUT5/OUT3 < 70% of the
nominal value
T
J
> +150°C
Conditions
Doc ID 11674 Rev 8
L
=
V
IN
f
sw
LGATE5/LGATE3 pin is forced high, LDO5 remains
active. Exit by a power on reset or toggling SHDN or
EN5/EN3
LGATE5/LGATE3 is forced high after the soft end
mode, LDO5 remains active. Exit by a power on reset
or toggling SHDN or EN5/EN3
All circuitry off. Exit by a POR on VIN or toggling
SHDN.
−
×
V
Δ
OUT
I
L
×
V
V
OUT
IN
Description
PM6685